Git Product home page Git Product logo

ctobjectivecruntimeadditions's Introduction

CTObjectiveCRuntimeAdditions

Some Objective-C runtime additions.

Swizzeling methods with blocks

If you wanted to swizzle a method before, you would have to declare a category on a class (usually resulting in two extra files).

CTObjectiveCRuntimeAdditions introduces a new method void class_swizzleSelectorWithBlock(Class class, SEL originalSelector, SEL unusedSelector, id block); which takes the class, the selector you want to swizzle, an unused selector in which the previous implementation will be stored and a block that will be called instead of the original implementation.

The block must come with a defined argument list as follows:

  • return type of previous implemention must match the return type of the block.
  • first argument must be an object which will be self
  • second argument must be an implementation pointer, which will be passed to the block to be able to call the previous implementation
  • further arguments must be the as of the original implementation after its SEL _cmd argument

Example:

If we take the following class as an example

@interface CTTestSwizzleClass : NSObject {

- (NSString *)helloWorldStringFromString:(NSString *)string;

@end

@implementation CTTestSwizzleClass

- (NSString *)helloWorldStringFromString:(NSString *)string
{
    return [@"Hello World" stringByAppendingFormat:@" %@", string];
}

@end

one could swizzle the selector @selector(helloWorldStringFromString:) as follows:

class_swizzleSelectorWithBlock([CTTestSwizzleClass class], @selector(helloWorldStringFromString:), @selector(__hookedHelloWorldStringFromString:), ^NSString *(CTTestSwizzleClass *blockSelf, IMP originalImplementation, NSString *string) {
    return [originalImplementation(blockSelf, @selector(__hookedHelloWorldStringFromString:), string) stringByAppendingFormat:@" Hooked"];
});

Now the following code

CTTestSwizzleClass *testObject = [[CTTestSwizzleClass alloc] init];
NSLog(@"%@", [testObject helloWorldStringFromString:@"Oli"]);

would produce the output Hello World Oli Hooked instead of just Hello World Oli.

Getting runtime information about blocks

CTBlockDescription lets you inspect blocks including arguments and compile time features at runtime.

One could use CTBlockDescription for the following test block:

// a test block.
BOOL(^testBlock)(BOOL animated, id object) = ^BOOL(BOOL animated, id object) {
    return YES;
};

// allocating a block description
CTBlockDescription *blockDescription = [[CTBlockDescription alloc] initWithBlock:testBlock];

// getting a method signature for this block
NSMethodSignature *methodSignature = blockDescription.blockSignature;
/**
<NSMethodSignature: 0x253f080>
    number of arguments = 3
    frame size = 12
    is special struct return? NO
    return value: -------- -------- -------- --------
        type encoding (c) 'c'
        flags {isSigned}
        modifiers {}
        frame {offset = 0, offset adjust = 0, size = 4, size adjust = -3}
        memory {offset = 0, size = 1}
    argument 0: -------- -------- -------- --------
        type encoding (@) '@?'
        flags {isObject, isBlock}
        modifiers {}
        frame {offset = 0, offset adjust = 0, size = 4, size adjust = 0}
        memory {offset = 0, size = 4}
    argument 1: -------- -------- -------- --------
        type encoding (c) 'c'
        flags {isSigned}
        modifiers {}
        frame {offset = 4, offset adjust = 0, size = 4, size adjust = -3}
        memory {offset = 0, size = 1}
    argument 2: -------- -------- -------- --------
        type encoding (@) '@'
        flags {isObject}
        modifiers {}
        frame {offset = 8, offset adjust = 0, size = 4, size adjust = 0}
        memory {offset = 0, size = 4}
*/

License

MIT

Thanks goes to the Block Implementation Specification and the A2DynamicDelegate project for some good libffi samples and convertion from encodings to libffi types.

ctobjectivecruntimeadditions's People

Contributors

oliverletterer avatar

Watchers

 avatar  avatar

Recommend Projects

  • React photo React

    A declarative, efficient, and flexible JavaScript library for building user interfaces.

  • Vue.js photo Vue.js

    ๐Ÿ–– Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.

  • Typescript photo Typescript

    TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

  • TensorFlow photo TensorFlow

    An Open Source Machine Learning Framework for Everyone

  • Django photo Django

    The Web framework for perfectionists with deadlines.

  • D3 photo D3

    Bring data to life with SVG, Canvas and HTML. ๐Ÿ“Š๐Ÿ“ˆ๐ŸŽ‰

Recommend Topics

  • javascript

    JavaScript (JS) is a lightweight interpreted programming language with first-class functions.

  • web

    Some thing interesting about web. New door for the world.

  • server

    A server is a program made to process requests and deliver data to clients.

  • Machine learning

    Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.

  • Game

    Some thing interesting about game, make everyone happy.

Recommend Org

  • Facebook photo Facebook

    We are working to build community through open source technology. NB: members must have two-factor auth.

  • Microsoft photo Microsoft

    Open source projects and samples from Microsoft.

  • Google photo Google

    Google โค๏ธ Open Source for everyone.

  • D3 photo D3

    Data-Driven Documents codes.