XCProject* project = [[XCProject alloc] initWithFilePath:@"MyProject.xcodeproj"];
XCGroup* group = [project groupWithPathFromRoot:@"Main"];
XCClassDefinition* classDefinition = [[XCClassDefinition alloc] initWithName:@"MyNewClass"];
[classDefinition setHeader:@"<some-header-text>"];
[classDefinition setSource:@"<some-impl-text>"];

[group addClass:classDefinition];
[project save];

XCTarget* target = [project targetWithName:@"SomeTarget"];
XCTarget* duplicated = [target duplicateWithTargetName:@"DuplicatedTarget" productName:@"NewProduct"];

XCSourceFile* sourceFile = [project fileWithName:@"MyNewClass.m"];
XCTarget* examples = [project targetWithName:@"Examples"];
[examples addMember:sourceFile];
[project save];

XCXibDefinition* xibDefinition = [[XCXibDefinition alloc] initWithName:@"MyXibFile" content:@"<xibXml>"];
[group addXib:xibDefinition toTargets:[project targets]];
[project save];

XCFrameworkDefinition* frameworkDefinition =
    [[XCFrameworkDefinition alloc] initWithFilePath:@"<framework path>" copyToDestination:NO];
[group addFramework:frameworkDefinition toTargets:[project targets]];
[project save];

XCSourceFileDefinition* sourceFileDefinition = [[XCSourceFileDefinition alloc]
    initWithName:@"MyImageFile.png" data:[NSData dataWithContentsOfFile:<your image file name>]
    type:ImageResourcePNG];

[group addSourceFile:sourceFileDefinition];
[project save];

XCSourceFileDefinition* sourceFileDefinition = [XCSourceFileDefinition sourceDefinitionWithAssetCatalogName:<path to asset catalog>];

[group addSourceFile:sourceFileDefinition];
[project save];

XCSourceFileDefinition* header = [[XCSourceFileDefinition alloc]
    initWithName:@"SomeHeader.h" text:<your header text> type:SourceCodeHeader];

[group addSourceFile:header];
[project save];

subProjectDefinition = [XCSubProjectDefinition withName:@"mySubproject" projPath=@"/Path/To/Subproject" type:XcodeProject];
[group addSubProject:subProjectDefinition toTargets:[project targets]];

[group removeSubProject:subProjectDefinition];  //TODO: project should be able to remove itself from parent.

XCTarget* target = [_project targetWithName:_projectName];
for (NSString* configName in [target configurations])
{
    XCBuildConfiguration* configuration = [target configurationWithName:configName];
    NSMutableArray* headerPaths = [[NSMutableArray alloc] init];
    [headerPaths addObject:@"$(inherited)"];
    [headerPaths addObject:@"$(SRCROOT)/include"];        
    [configuration addOrReplaceSetting:headerPaths forKey:@"HEADER_SEARCH_PATHS"];
}

XCSourceFile * libSourceFile = [project fileWithName:@"libAmazing.a"];

XCTarget* target = [project targetWithName:self.mProject.projectName];
[target addMember:libSourceFile];

for (NSString* configName in [target configurations]) {
    XCProjectBuildConfig* configuration = [target configurationWithName:configName];
    NSMutableArray* headerPaths = [[NSMutableArray alloc] init];
    [headerPaths addObject:@"$(inherited)"];
    [headerPaths addObject:@"$(PROJECT_DIR)/Amazing"];
    [configuration addOrReplaceSetting:headerPaths forKey:@"LIBRARY_SEARCH_PATHS"];
}

//Creates the reference in the project and writes the contents to disk. If a file already exists at the 
//specified location, its contents will be updated.
[definition setFileOperationStyle:FileOperationStyleOverwrite]; 

//Creates the reference in the project. If a file already exists at the specified location, the contents will 
//not be updated.
[definition setFileOperationStyle:FileOperationStyleAcceptExisting]; 

//Creates the reference in the project, but does not write to disk. The filesystem is expected to be updated 
//through some other means.
[definition setFileOperationStyle:FileOperationStyleReferenceOnly];