diff --git a/docs/.vitepress/config.mts b/docs/.vitepress/config.mts
index 00da618..18c937b 100644
--- a/docs/.vitepress/config.mts
+++ b/docs/.vitepress/config.mts
@@ -42,12 +42,13 @@ export default defineConfig({
     sidebar: [
       { text: "Intro", link: "/" },
       { text: "Use-Cases", link: "/use-case" },
+      { text: "Error early", link: "/guide/error-early" },
       {
         text: "Guides",
         items: [
           { text: "Getting Started", link: "/guide/getting-started" },
           { text: "Installation", link: "/guide/install" },
-          { text: "Error early", link: "/guide/error-early" },
+          { text: "Input/Output formats", link: "/guide/format" },
           { text: "Convert Enums", link: "/guide/enum" },
           {
             text: "Output into same package",
@@ -77,7 +78,7 @@ export default defineConfig({
           { text: "Settings Overview", link: "/reference/settings" },
           { text: "Enums", link: "/reference/enum" },
           {
-            text: "Converter",
+            text: "Conversion",
             collapsed: true,
             items: [
               { text: "converter", link: "/reference/converter" },
@@ -85,6 +86,7 @@ export default defineConfig({
               { text: "name", link: "/reference/name" },
               { text: "output", link: "/reference/output" },
               { text: "struct", link: "/reference/struct" },
+              { text: "variables", link: "/reference/variables" },
             ],
           },
           {
diff --git a/docs/changelog.md b/docs/changelog.md
index 1ea6be1..5144154 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -6,7 +6,12 @@ import GH from './GH.vue';
 
 ## unreleased
 
-- tbd
+- Add two input-output formats. See
+  [Guide: Input/Output formats](guide/format.md) for help to choose a format.
+  The new formats allow you to call top level functions without the need to
+  instantiate a struct to call methods on it. <GH issue="77" pr="149"/>
+  - Add [`variables`](reference/variables.md) setting
+  - Add [`output:format`](reference/output.md#output-format) setting
 
 ## v1.4.1
 
diff --git a/docs/guide/format.md b/docs/guide/format.md
new file mode 100644
index 0000000..8561aa1
--- /dev/null
+++ b/docs/guide/format.md
@@ -0,0 +1,78 @@
+# Input and output formats
+
+Goverter supports three different input output format combinations. This guide
+is for you to decide the formats you want to use. All examples have this in
+common.
+
+[[toc]]
+
+## interface to struct
+
+This is the default when using
+[`goverter:converter`](../reference/converter.md).
+
+**Pros**:
+
+- All goverter features are supported
+- The interface is usable before goverter generated the implementation.
+  - reduces the occurence of compile errors because of missing or outdated
+  generated implementation.
+  - allows using generated methods in custom methods
+
+**Cons**:
+
+- You need to initialize the implementation.
+- You need to call methods on the struct to execute conversions
+
+::: details Example (click me)
+::: code-group
+<<< @../../example/format/interfacetostruct/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/interfacetostruct/generated/generated.go [generated/generated.go]
+:::
+
+## variables to assign-variable
+
+This is the default when using
+[`goverter:variables`](../reference/converter.md).
+
+**Pros**:
+
+- All goverter features are supported.
+- The variables are usable before goverter generated the implementation.
+  - reduces the occurence of compile errors because of missing or outdated
+    generated implementation.
+  - allows using generated functions in custom methods
+- You can execute conversions directly without having to initializing a struct
+
+**Cons**:
+
+- Possible runtime overhead when Go cannot optimizen variables the same as
+  functions. Benchmark your use-case, if speed is really important to you.
+
+::: details Example (click me)
+::: code-group
+<<< @../../example/format/assignvariables/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/assignvariables/input.gen.go
+:::
+
+## interface to functions
+
+**Pros**:
+
+- You can execute conversions directly without having to initializing a struct
+
+**Cons**:
+
+- The interface is only used for defining the conversions and is otherwise not
+  usable
+- The use-case [`map` method with converter](../reference/map.md#method-with-converter) is
+  unsupported without replacement.
+
+::: details Example (click me)
+::: code-group
+<<< @../../example/format/interfacefunction/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/interfacefunction/generated/generated.go
+:::
diff --git a/docs/reference/define-settings.md b/docs/reference/define-settings.md
index 7ed6b3a..46fe216 100644
--- a/docs/reference/define-settings.md
+++ b/docs/reference/define-settings.md
@@ -28,9 +28,10 @@ type Converter interface {
 
 the resolved settings would be the same as with the example below for Converter.
 
-## Converter
+## Conversion
 
-You can define settings on the converter interface by prefixing them with `goverter:`.
+When using [`goverter:converter`](converter.md), then can define settings on the
+converter interface by prefixing them with `goverter:`.
 
 ```go
 // goverter:converter
@@ -41,9 +42,22 @@ type Converter interface {
 }
 ```
 
+When using [`goverter:variables`](variables.md), then can define settings on the
+`var`-block by prefixing them with `goverter:`.
+
+```go
+// goverter:variables
+// goverter:setting yes
+// goverter:setting2 no
+var (
+    Convert func(source Input) Output
+)
+```
+
 ## Method
 
-You can define settings on the converter methods by prefixing them with `goverter:`.
+When using [`goverter:converter`](converter.md), then you can define settings
+on the converter methods by prefixing them with `goverter:`.
 
 ```go
 // goverter:converter
@@ -54,6 +68,18 @@ type Converter interface {
 }
 ```
 
+When using [`goverter:variables`](variables.md), then can define settings on the
+function variables by prefixing them with `goverter:`.
+
+```go
+// goverter:variables
+var (
+    // goverter:setting yes
+    // goverter:setting2 no
+    Convert func(source Input) Output
+)
+```
+
 ### Inheritance
 
 Method settings can be inherited for all methods if they are defined on the CLI
diff --git a/docs/reference/enum.md b/docs/reference/enum.md
index 519159f..4e6484e 100644
--- a/docs/reference/enum.md
+++ b/docs/reference/enum.md
@@ -10,7 +10,7 @@ type](https://go.dev/ref/spec#Underlying_types) of (`float`, `string`, or
 ## enum
 
 `enum [yes|no]` can be defined as [CLI argument](./define-settings.md#cli) or
-[converter comment](./define-settings.md#converter). `enum` is enabled per
+[conversion comment](./define-settings.md#conversion). `enum` is enabled per
 default.
 
 `enum` allows you to disable enum support in goverter.
diff --git a/docs/reference/extend.md b/docs/reference/extend.md
index c6fd141..058a999 100644
--- a/docs/reference/extend.md
+++ b/docs/reference/extend.md
@@ -1,7 +1,7 @@
 # Setting: extend
 
 `extend [PACKAGE:]TYPE...` can be defined as [CLI argument](./define-settings.md#cli) or
-[converter comment](./define-settings.md#converter).
+[conversion comment](./define-settings.md#conversion).
 
 If a type cannot be converted automatically, you can manually define an
 implementation with `:extend` for the missing mapping. Keep in mind,
diff --git a/docs/reference/matchIgnoreCase.md b/docs/reference/matchIgnoreCase.md
index d0e1fd3..7a9062d 100644
--- a/docs/reference/matchIgnoreCase.md
+++ b/docs/reference/matchIgnoreCase.md
@@ -3,7 +3,7 @@
 `matchIgnoreCase [yes,no]` is a
 [boolean setting](./define-settings.md#boolean) and can be defined as
 [CLI argument](./define-settings.md#cli),
-[converter comment](./define-settings.md#converter) or
+[conversion comment](./define-settings.md#conversion) or
 [method comment](./define-settings.md#method). This setting is
 [inheritable](./define-settings.md#inheritance).
 
diff --git a/docs/reference/name.md b/docs/reference/name.md
index 50efad4..b70644f 100644
--- a/docs/reference/name.md
+++ b/docs/reference/name.md
@@ -1,7 +1,7 @@
 # Setting: name
 
 `name NAME` can be defined as [CLI argument](./define-settings.md#cli) or
-[converter comment](./define-settings.md#converter).
+[conversion comment](./define-settings.md#conversion).
 
 `name` instructs goverter to use the given *name* for the generated struct. By
 default goverter will use the interface name and append `Impl` at the end.
diff --git a/docs/reference/output.md b/docs/reference/output.md
index f26cc94..27a8d17 100644
--- a/docs/reference/output.md
+++ b/docs/reference/output.md
@@ -1,9 +1,11 @@
 # Setting: output
 
+[[toc]]
+
 ## output:file
 
 `output:file FILE` can be defined as [CLI argument](./define-settings.md#cli) or
-[converter comment](./define-settings.md#converter). Default is
+[conversion comment](./define-settings.md#conversion). Default is
 `./generated/generated.go`.
 
 `output:file` sets the generated output file of a converter interface. The file
@@ -28,10 +30,50 @@ the same. See this more complex example:
 <<< @../../example/output-multiple-files/b/generated.go [b/generated.go]
 :::
 
+## output:format
+
+`output:format FORMAT` can be defined as [CLI argument](./define-settings.md#cli) or
+[conversion comment](./define-settings.md#conversion). Default `struct`
+
+Specify the output FORMAT for the conversion methods. See [Guide: Input/Output formats](../guide/format.md)
+
+### output:format struct
+
+Output an implementation of the conversion interface by creating a struct with methods.
+
+::: details Example (click me)
+::: code-group
+<<< @../../example/format/interfacetostruct/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/interfacetostruct/generated/generated.go [generated/generated.go]
+:::
+
+### output:format assign-variable
+
+Output an init function assiging an implementation for all function variables.
+
+::: details Example (click me)
+::: code-group
+<<< @../../example/format/assignvariables/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/assignvariables/input.gen.go
+:::
+
+### output:format function
+
+Output a function for each method in the conversion interface.
+
+::: details Example (click me)
+::: code-group
+<<< @../../example/format/interfacefunction/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/interfacefunction/generated/generated.go [generated/generated.go]
+:::
+
 ## output:package
 
 `output:package [PACKAGE][:NAME]` can be defined as
-[CLI argument](./define-settings.md#cli) or [converter comment](./define-settings.md#converter).
+[CLI argument](./define-settings.md#cli) or [conversion comment](./define-settings.md#conversion).
 Default is `:generated`.
 
 ### output:package PACKAGE
diff --git a/docs/reference/settings.md b/docs/reference/settings.md
index e500886..f4e344f 100644
--- a/docs/reference/settings.md
+++ b/docs/reference/settings.md
@@ -4,10 +4,10 @@ Before configuring settings here it is useful to understand how [converter
 generation works](../explanation/generation.md) and how to [configure nested
 settings](../guide/configure-nested.md).
 
-## Converter
+## Conversion
 
 These settings can only be defined as [CLI argument](./define-settings.md#cli) or
-[converter comment](./define-settings.md#converter).
+[conversion comment](./define-settings.md#conversion).
 
 - [`converter` marker comment for conversion interfaces](./converter.md)
 - [`enum [yes|no]` enable / disable enum support](./enum.md#enum-detect)
@@ -17,8 +17,9 @@ These settings can only be defined as [CLI argument](./define-settings.md#cli) o
 - [`output:file FILE` set the output directory for a converter](./output.md#outputfile)
 - [`output:package [PACKAGE:]NAME` set the output package for a converter](./output.md#outputpackage)
 - [`struct:comment COMMENT` add comments to generated struct](./struct.md#structcomment-comment)
+- [`variables` marker comment for variable blocks](./variables.md)
 
-## Method:
+## Method
 
 These settings can only be defined as [method comment](./define-settings.md#method).
 
@@ -38,7 +39,7 @@ These settings can only be defined as [method comment](./define-settings.md#meth
 ### Method (inheritable)
 
 These settings can be defined as [CLI argument](./define-settings.md#cli),
-[converter comment](./define-settings.md#converter) or
+[conversion comment](./define-settings.md#conversion) or
 [method comment](./define-settings.md#method) and are
 [inheritable](./define-settings.md#inheritance).
 
diff --git a/docs/reference/struct.md b/docs/reference/struct.md
index 712fdc7..dcd7bd5 100644
--- a/docs/reference/struct.md
+++ b/docs/reference/struct.md
@@ -3,7 +3,7 @@
 ## struct:comment COMMENT
 
 `struct:comment COMMENT` can be defined as [CLI argument](./define-settings.md#cli)
-or [converter comment](./define-settings.md#converter).
+or [conversion comment](./define-settings.md#conversion).
 
 `struct:comment` instructs goverter to add a comment line to the generated
 struct. It can be configured multiple times to add multiline comments. Prefix
diff --git a/docs/reference/useUnderlyingTypeMethods.md b/docs/reference/useUnderlyingTypeMethods.md
index 7a6eb84..a870f47 100644
--- a/docs/reference/useUnderlyingTypeMethods.md
+++ b/docs/reference/useUnderlyingTypeMethods.md
@@ -3,7 +3,7 @@
 `useUnderlyingTypeMethods [yes,no]` is a
 [boolean setting](./define-settings.md#boolean) and can be defined as
 [CLI argument](./define-settings.md#cli),
-[converter comment](./define-settings.md#converter) or
+[conversion comment](./define-settings.md#conversion) or
 [method comment](./define-settings.md#method). This setting is
 [inheritable](./define-settings.md#inheritance).
 
diff --git a/docs/reference/useZeroValueOnPointerInconsistency.md b/docs/reference/useZeroValueOnPointerInconsistency.md
index a262778..3d000a4 100644
--- a/docs/reference/useZeroValueOnPointerInconsistency.md
+++ b/docs/reference/useZeroValueOnPointerInconsistency.md
@@ -3,7 +3,7 @@
 `useZeroValueOnPointerInconsistency [yes,no]` is a
 [boolean setting](./define-settings.md#boolean) and can be defined as
 [CLI argument](./define-settings.md#cli),
-[converter comment](./define-settings.md#converter) or
+[conversion comment](./define-settings.md#conversion) or
 [method comment](./define-settings.md#method). This setting is
 [inheritable](./define-settings.md#inheritance).
 
diff --git a/docs/reference/variables.md b/docs/reference/variables.md
new file mode 100644
index 0000000..f86de96
--- /dev/null
+++ b/docs/reference/variables.md
@@ -0,0 +1,16 @@
+# Setting: converter
+
+`variables` accepts no arguments and can be defined as [converter
+comment](./define-settings.md#converter).
+
+`variables` instructs goverter to generate an implementation for the given
+variables. You can have multiple variables blocks in one package.
+
+See [output](./output.md) to control the output location/package of the
+generated converter.
+
+::: code-group
+<<< @../../example/format/assignvariables/input.go
+<<< @../../example/format/common/common.go
+<<< @../../example/format/assignvariables/input.gen.go
+:::
diff --git a/docs/reference/wrapErrors.md b/docs/reference/wrapErrors.md
index cdeaefd..1bb34fc 100644
--- a/docs/reference/wrapErrors.md
+++ b/docs/reference/wrapErrors.md
@@ -3,7 +3,7 @@
 `wrapErrors [yes,no]` is a
 [boolean setting](./define-settings.md#boolean) and can be defined as
 [CLI argument](./define-settings.md#cli),
-[converter comment](./define-settings.md#converter) or
+[conversion comment](./define-settings.md#conversion) or
 [method comment](./define-settings.md#method). This setting is
 [inheritable](./define-settings.md#inheritance).
 
diff --git a/docs/reference/wrapErrorsUsing.md b/docs/reference/wrapErrorsUsing.md
index 5838de0..00b1cbf 100644
--- a/docs/reference/wrapErrorsUsing.md
+++ b/docs/reference/wrapErrorsUsing.md
@@ -2,7 +2,7 @@
 
 `wrapErrorsUsing [PACKAGE]` is a [boolean setting](./define-settings.md#boolean)
 and can be defined as [CLI argument](./define-settings.md#cli),
-[converter comment](./define-settings.md#converter) or
+[conversion comment](./define-settings.md#conversion) or
 [method comment](./define-settings.md#method). This setting is
 [inheritable](./define-settings.md#inheritance).
 
diff --git a/example/format/assignvariables/input.gen.go b/example/format/assignvariables/input.gen.go
new file mode 100644
index 0000000..9b69f6f
--- /dev/null
+++ b/example/format/assignvariables/input.gen.go
@@ -0,0 +1,48 @@
+// Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+//go:build !goverter
+
+package house
+
+import common "github.com/jmattheis/goverter/example/format/common"
+
+func init() {
+	ConvertApartment = func(source common.DBApartment) common.APIApartment {
+		var commonAPIApartment common.APIApartment
+		commonAPIApartment.Position = source.Position
+		commonAPIApartment.Owner = ConvertPerson(source.Owner)
+		commonAPIApartment.OwnerName = source.Owner.Name
+		if source.CoResident != nil {
+			commonAPIApartment.CoResident = make([]common.APIPerson, len(source.CoResident))
+			for i := 0; i < len(source.CoResident); i++ {
+				commonAPIApartment.CoResident[i] = ConvertPerson(source.CoResident[i])
+			}
+		}
+		return commonAPIApartment
+	}
+	ConvertHouse = func(source common.DBHouse) common.APIHouse {
+		var commonAPIHouse common.APIHouse
+		commonAPIHouse.Address = source.Address
+		commonAPIHouse.Apartments = ConvertToApartmentMap(source.Apartments)
+		return commonAPIHouse
+	}
+	ConvertPerson = func(source common.DBPerson) common.APIPerson {
+		var commonAPIPerson common.APIPerson
+		commonAPIPerson.ID = source.ID
+		commonAPIPerson.MiddleName = SQLStringToPString(source.MiddleName)
+		pString := source.Name
+		commonAPIPerson.FirstName = &pString
+		if source.Friends != nil {
+			commonAPIPerson.Friends = make([]common.APIPerson, len(source.Friends))
+			for i := 0; i < len(source.Friends); i++ {
+				commonAPIPerson.Friends[i] = ConvertPerson(source.Friends[i])
+			}
+		}
+		commonAPIPerson.Info = commonInfoToCommonInfo(source.Info)
+		return commonAPIPerson
+	}
+}
+func commonInfoToCommonInfo(source common.Info) common.Info {
+	var commonInfo common.Info
+	commonInfo.Birthplace = source.Birthplace
+	return commonInfo
+}
diff --git a/example/format/assignvariables/input.go b/example/format/assignvariables/input.go
new file mode 100644
index 0000000..ce3bf0d
--- /dev/null
+++ b/example/format/assignvariables/input.go
@@ -0,0 +1,35 @@
+package house
+
+import (
+	"database/sql"
+
+	"github.com/jmattheis/goverter/example/format/common"
+)
+
+// goverter:variables
+// goverter:output:format assign-variable
+// goverter:extend SQLStringToPString
+// goverter:extend ConvertToApartmentMap
+var (
+	ConvertHouse func(source common.DBHouse) common.APIHouse
+	// goverter:map Name FirstName
+	// goverter:ignore Age
+	ConvertPerson func(source common.DBPerson) common.APIPerson
+	// goverter:map Owner.Name OwnerName
+	ConvertApartment func(source common.DBApartment) common.APIApartment
+)
+
+func SQLStringToPString(value sql.NullString) *string {
+	if value.Valid {
+		return &value.String
+	}
+	return nil
+}
+
+func ConvertToApartmentMap(source []common.DBApartment) map[uint]common.APIApartment {
+	m := make(map[uint]common.APIApartment)
+	for _, apartment := range source {
+		m[apartment.Position] = ConvertApartment(apartment) // !! this is not supported in some formats
+	}
+	return m
+}
diff --git a/example/format/common/common.go b/example/format/common/common.go
new file mode 100644
index 0000000..25fb304
--- /dev/null
+++ b/example/format/common/common.go
@@ -0,0 +1,47 @@
+package common
+
+import "database/sql"
+
+type DBHouse struct {
+	Address    string
+	Apartments []DBApartment
+}
+
+type DBApartment struct {
+	Position   uint
+	Owner      DBPerson
+	CoResident []DBPerson
+}
+
+type DBPerson struct {
+	ID         int
+	Name       string
+	MiddleName sql.NullString
+	Friends    []DBPerson
+	Info       Info
+}
+
+type APIHouse struct {
+	Address    string
+	Apartments map[uint]APIApartment
+}
+
+type APIApartment struct {
+	Position   uint
+	Owner      APIPerson
+	OwnerName  string
+	CoResident []APIPerson
+}
+
+type APIPerson struct {
+	ID         int
+	MiddleName *string
+	FirstName  *string
+	Friends    []APIPerson
+	Info       Info
+	Age        int
+}
+
+type Info struct {
+	Birthplace string
+}
diff --git a/example/format/interfacefunction/generated/generated.go b/example/format/interfacefunction/generated/generated.go
new file mode 100644
index 0000000..375e50b
--- /dev/null
+++ b/example/format/interfacefunction/generated/generated.go
@@ -0,0 +1,43 @@
+// Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+//go:build !goverter
+
+package generated
+
+import (
+	common "github.com/jmattheis/goverter/example/format/common"
+	interfacefunction "github.com/jmattheis/goverter/example/format/interfacefunction"
+)
+
+func ConvertApartment(source common.DBApartment) common.APIApartment {
+	var commonAPIApartment common.APIApartment
+	commonAPIApartment.Position = source.Position
+	commonAPIApartment.Owner = ConvertPerson(source.Owner)
+	commonAPIApartment.OwnerName = source.Owner.Name
+	if source.CoResident != nil {
+		commonAPIApartment.CoResident = make([]common.APIPerson, len(source.CoResident))
+		for i := 0; i < len(source.CoResident); i++ {
+			commonAPIApartment.CoResident[i] = ConvertPerson(source.CoResident[i])
+		}
+	}
+	return commonAPIApartment
+}
+func ConvertPerson(source common.DBPerson) common.APIPerson {
+	var commonAPIPerson common.APIPerson
+	commonAPIPerson.ID = source.ID
+	commonAPIPerson.MiddleName = interfacefunction.SQLStringToPString(source.MiddleName)
+	pString := source.Name
+	commonAPIPerson.FirstName = &pString
+	if source.Friends != nil {
+		commonAPIPerson.Friends = make([]common.APIPerson, len(source.Friends))
+		for i := 0; i < len(source.Friends); i++ {
+			commonAPIPerson.Friends[i] = ConvertPerson(source.Friends[i])
+		}
+	}
+	commonAPIPerson.Info = commonInfoToCommonInfo(source.Info)
+	return commonAPIPerson
+}
+func commonInfoToCommonInfo(source common.Info) common.Info {
+	var commonInfo common.Info
+	commonInfo.Birthplace = source.Birthplace
+	return commonInfo
+}
diff --git a/example/format/interfacefunction/input.go b/example/format/interfacefunction/input.go
new file mode 100644
index 0000000..151e1db
--- /dev/null
+++ b/example/format/interfacefunction/input.go
@@ -0,0 +1,25 @@
+package house
+
+import (
+	"database/sql"
+
+	"github.com/jmattheis/goverter/example/format/common"
+)
+
+// goverter:converter
+// goverter:output:format function
+// goverter:extend SQLStringToPString
+type Converter interface {
+	// goverter:map Owner.Name OwnerName
+	ConvertApartment(source common.DBApartment) common.APIApartment
+	// goverter:map Name FirstName
+	// goverter:ignore Age
+	ConvertPerson(source common.DBPerson) common.APIPerson
+}
+
+func SQLStringToPString(value sql.NullString) *string {
+	if value.Valid {
+		return &value.String
+	}
+	return nil
+}
diff --git a/example/format/interfacetostruct/generated/generated.go b/example/format/interfacetostruct/generated/generated.go
new file mode 100644
index 0000000..d30b27e
--- /dev/null
+++ b/example/format/interfacetostruct/generated/generated.go
@@ -0,0 +1,51 @@
+// Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+//go:build !goverter
+
+package generated
+
+import (
+	common "github.com/jmattheis/goverter/example/format/common"
+	interfacetostruct "github.com/jmattheis/goverter/example/format/interfacetostruct"
+)
+
+type ConverterImpl struct{}
+
+func (c *ConverterImpl) ConvertApartment(source common.DBApartment) common.APIApartment {
+	var commonAPIApartment common.APIApartment
+	commonAPIApartment.Position = source.Position
+	commonAPIApartment.Owner = c.ConvertPerson(source.Owner)
+	commonAPIApartment.OwnerName = source.Owner.Name
+	if source.CoResident != nil {
+		commonAPIApartment.CoResident = make([]common.APIPerson, len(source.CoResident))
+		for i := 0; i < len(source.CoResident); i++ {
+			commonAPIApartment.CoResident[i] = c.ConvertPerson(source.CoResident[i])
+		}
+	}
+	return commonAPIApartment
+}
+func (c *ConverterImpl) ConvertHouse(source common.DBHouse) common.APIHouse {
+	var commonAPIHouse common.APIHouse
+	commonAPIHouse.Address = source.Address
+	commonAPIHouse.Apartments = interfacetostruct.ConvertToApartmentMap(c, source.Apartments)
+	return commonAPIHouse
+}
+func (c *ConverterImpl) ConvertPerson(source common.DBPerson) common.APIPerson {
+	var commonAPIPerson common.APIPerson
+	commonAPIPerson.ID = source.ID
+	commonAPIPerson.MiddleName = interfacetostruct.SQLStringToPString(source.MiddleName)
+	pString := source.Name
+	commonAPIPerson.FirstName = &pString
+	if source.Friends != nil {
+		commonAPIPerson.Friends = make([]common.APIPerson, len(source.Friends))
+		for i := 0; i < len(source.Friends); i++ {
+			commonAPIPerson.Friends[i] = c.ConvertPerson(source.Friends[i])
+		}
+	}
+	commonAPIPerson.Info = c.commonInfoToCommonInfo(source.Info)
+	return commonAPIPerson
+}
+func (c *ConverterImpl) commonInfoToCommonInfo(source common.Info) common.Info {
+	var commonInfo common.Info
+	commonInfo.Birthplace = source.Birthplace
+	return commonInfo
+}
diff --git a/example/format/interfacetostruct/input.go b/example/format/interfacetostruct/input.go
new file mode 100644
index 0000000..dd1540d
--- /dev/null
+++ b/example/format/interfacetostruct/input.go
@@ -0,0 +1,35 @@
+package house
+
+import (
+	"database/sql"
+
+	"github.com/jmattheis/goverter/example/format/common"
+)
+
+// goverter:converter
+// goverter:output:format struct
+// goverter:extend SQLStringToPString
+// goverter:extend ConvertToApartmentMap
+type Converter interface {
+	ConvertHouse(source common.DBHouse) common.APIHouse
+	// goverter:map Owner.Name OwnerName
+	ConvertApartment(source common.DBApartment) common.APIApartment
+	// goverter:map Name FirstName
+	// goverter:ignore Age
+	ConvertPerson(source common.DBPerson) common.APIPerson
+}
+
+func SQLStringToPString(value sql.NullString) *string {
+	if value.Valid {
+		return &value.String
+	}
+	return nil
+}
+
+func ConvertToApartmentMap(c Converter, source []common.DBApartment) map[uint]common.APIApartment {
+	m := make(map[uint]common.APIApartment)
+	for _, apartment := range source {
+		m[apartment.Position] = c.ConvertApartment(apartment) // !! this is not supported in some formats
+	}
+	return m
+}