Util class for doing reflection via objc runtime

ReflectionUtil

//
//  ReflectionUtil.m
//
//  Created by Rhishikesh Joshi on 02/09/15.
//

#import "ReflectionUtil.h"
@import ObjectiveC;

@implementation ReflectionUtil

+ (void) callVoidClassMethod:(NSString *)methodName onClass:(NSString *)className withArgs:(NSArray *) args {
    id reflectionClass = [[NSBundle mainBundle] classNamed:className];
    if(reflectionClass) {
        Class class = NSClassFromString(className);
        SEL selector = NSSelectorFromString(methodName);

        NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[class methodSignatureForSelector:selector]];
        [inv setSelector:selector];
        [inv setTarget:class];
        int position = 2;
        //arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation
        for (id arg in args) {
            [inv setArgument:&arg atIndex:position];
            position++;
        }
        [inv invoke];
    }
}

+ (void) callVoidInstanceMethod:(NSString *)methodName onInstance:(id) object withArgs:(NSArray *) args {
    if(object) {
        SEL selector = NSSelectorFromString(methodName);
        NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[object methodSignatureForSelector:selector]];
        [inv setSelector:selector];
        [inv setTarget:object];
        int position = 2;
        //arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation
        for (id arg in args) {
            [inv setArgument:&arg atIndex:position];
            position++;
        }
        [inv invoke];
    }
}

+ (id) callInstanceMethod:(NSString *)methodName
               onInstance:(id) object
                 withArgs:(NSArray *) args {
    if(object) {
        SEL selector = NSSelectorFromString(methodName);
        NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[object methodSignatureForSelector:selector]];
        [inv setSelector:selector];
        [inv setTarget:object];
        int position = 2;
        //arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation
        for (id arg in args) {
            [inv setArgument:&arg atIndex:position];
            position++;
        }
        [inv invoke];
        __unsafe_unretained id result;
        [inv getReturnValue:&result];
        return result;
    }
    return nil;
}

@end


//Usage :
//    NSString *someString = @"String";
//    NSString *lowerString = [ReflectionUtil callInstanceMethod:@"lowercaseString" onInstance:someString withArgs:nil];
//    NSLog(@"String is %@", lowerString);