PBXProject.ReplaceFile

Заменяет указанный файл новым.

Путь к указанному файлу заменяется, а GUID старого файла сохраняется.

using UnityEditor;
using System.IO;
using UnityEditor.Callbacks;
using UnityEditor.iOS.Xcode;

public class Sample_ReplaceFile  
{
    [PostProcessBuild]
    public static void OnPostprocessBuild(BuildTarget buildTarget, string pathToBuiltProject)
    {

        // Stop processing if build target is not iOS
        if (buildTarget != BuildTarget.iOS)
            return;

        // Initialize PBXProject
        string projectPath = PBXProject.GetPBXProjectPath(pathToBuiltProject);
        PBXProject pbxProject = new PBXProject();
        pbxProject.ReadFromFile(projectPath);

        // Get the target GUID
        string targetGuid = pbxProject.GetUnityMainTargetGuid();

        // Get the GUID of the existing file you want to replace
        string existingFilePath = "Resources/oldExampleFile.txt";
        string existingFileGuid = pbxProject.FindFileGuidByProjectPath(existingFilePath);

        // Add the new file and get the GUID
        string newFilePath = "path/to/your/newExampleFile.txt";
        string newFileGuid = pbxProject.AddFile(newFilePath, "Resources/newExampleFile.txt", PBXSourceTree.Source);

        // Replace the existing file with the new file
        pbxProject.ReplaceFile(existingFileGuid, newFileGuid);
        
        // Apply changes to the pbxproj file
        pbxProject.WriteToFile(projectPath);
    }
}