Replacing arguments and handeling integers

[YumAlpha]

hello, im trying to modify fields in an object that is an argument in the given function.
im trying to go by the field of "id" that contains a integer and then replace the other fields which contain the model name as a string and i just cant figure out how to do it properly and i would like to ask for some help if possible 🙏🙏🙏 i just cant figure out how to turn the "id" field into an integer to compare and how to switch the strings properly

import "frida-il2cpp-bridge";
console.log("Loaded")

const assem = Il2Cpp.Domain.assembly('Assembly-CSharp').image;

assem.class('NPCModel').method('CreateNPCModel').implementation = function(data: Il2Cpp.Object)  {
    if (data.field('id').readInt() === 162) {
    console.log("here comes the original data");
    var before = (Il2Cpp.String.from(data.field('head_resource'))).toString();

    console.log(before)
    data.field('head_resource').value = Il2Cpp.String.from("model_name");
    var after = (Il2Cpp.String.from(data.field('head_resource'))).toString();
    console.log("here comes the changed data");
    console.log(after);
	}
  };

[YumAlpha]

so i remade it a little bit to this:

import "frida-il2cpp-bridge";
console.log("Loaded Frida-il2cpp-bridge");

const assem = Il2Cpp.Domain.assembly('Assembly-CSharp').image;
console.log("Loaded Assembly-CSharp");

const originalImplementation = assem.class('NPCModel').method('CreateNPCModel').implementation;

assem.class('NPCModel').method('CreateNPCModel').implementation = function(this: Il2Cpp.Class | Il2Cpp.Object, data: Il2Cpp.Object)  {
    console.log(`data: ${data}`);
    console.log(`data.field('id'): ${data.field('id')}`);
    console.log(`data.field('id').value: ${data.field('id').value}`);
    console.log(`data.field('head_resource'): ${data.field('head_resource')}`);
    console.log(`data.field('head_resource'): ${data.field('head_resource').value}`);


    data.field('id').value = 4656;
    const result = assem.class('NPCModel').method('CreateNPCModel').invoke(data);
    // <--- onLeave
    console.log(result); // <--- onLeave
    return !!result;     // <--- onLeave

};

but this is the output:

data: DBNpcInfoRow
data.field('id'): System.Int32 id; // 0x10
data.field('id').value: 26
data.field('head_resource'): System.String head_resource; // 0x48
data.field('head_resource'): ""
hero_npc_base_dealer_short001 (NPCModel)
**Error: expected a pointer**

I can't for the life of me figure out how to print the string from 'head_resource' (which is what i want to replace) and how to make it so that it will keep doing the function properly and not throw an error

[ExternalAddress4401]

console.log(`data.field('head_resource'): ${data.field('head_resource').value}`);

Is correct for printing out the field. If it returns an empty string then it's empty, that's all there is to it.

You haven't attached the dumped implementation but typically if you want to work like this you can do it like so.

assem.class('NPCModel').method('CreateNPCModel').implementation = function(this: Il2Cpp.Class | Il2Cpp.Object, data: Il2Cpp.Object)  {
    const result = this.method('CreateNPCModel').invoke(data); //this refers to the NPCModel class in this case
    return result;
};

Which will retain the original implementation. I'm not sure what you're trying to accomplish by returning !!result because you've called the method which gives you a valid return value for the method but then you've gone ahead and changed it to an invalid return value.

If you know a valid value for head_resource you can modify it like so to apply it.

assem.class('NPCModel').method('CreateNPCModel').implementation = function(this: Il2Cpp.Class | Il2Cpp.Object, data: Il2Cpp.Object)  {
    const result = this.method('CreateNPCModel').invoke(data);
    result.field('head_resource').value = Il2Cpp.String.from('new_head_resource'); //not sure this is documented anywhere but it's how you should handle string values
    return result;
};

Which should apply it every time this function is called.