Creating and using a class (including instance variables and methods) at runtime with Heliograph

Heliograph-CreateAndUseClass.m

#import <Heliograph/Heliograph.h>


static CGSize DummySizeImpl(NSObject *self, SEL cmd) {
    HGInstanceVariableMirror *ivar = [[reflect(self) classMirror] instanceVariableNamed:@"_rectIvar"];
    CGRect rect;
    HGStructureValueMirror *value = [ivar valueIn:self];
    [value readStructureValue:&rect];
    return rect.size;
}


HGClassMirror *class = [reflect([NSObject class]) addSubclassNamed:@"FooBarBaz"];
	
HGInstanceVariableMirror *ivar = [class addInstanceVariableNamed:@"_rectIvar" withEncoding:@encode(CGRect)];
NSString *methodEncoding = [NSString stringWithFormat: @"%s%s%s", @encode(CGSize), @encode(id), @encode(SEL)];
HGMethodMirror *method = [class addMethodNamed:NSSelectorFromString(@"size") withImplementation:(IMP)DummySizeImpl andEncoding:[methodEncoding UTF8String]];
	
[class registerClass];
	
id instance = [[[class mirroredClass] alloc] init];
[ivar setValue:[NSValue valueWithCGRect:CGRectMake(0, 0, 123, 456)] in:instance];
	
CGSize resultSize;
[method invokeOn:instance withArguments:@[] returnValue:&resultSize];
	
NSLog(@"%@", NSStringFromCGSize(resultSize));

// => {123, 456}