iOS runtime(二)

本文通過一個示例來介紹runtime的攔截替換方法的使用，該魔法主要用於給系統方法添加新的功能，示例爲系統按鈕的點擊事件增加了一個計算點擊次數的方法。

#import "UIButton+Count.h"
#import <objc/runtime.h>
#import "ZTools.h"

@implementation UIButton (Count)

+ (void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        
        Class selfClass = [self class];
        
        //原來的方法
        SEL oriSEL = @selector(sendAction:to:forEvent:);
        Method oriMethod = class_getInstanceMethod(selfClass, oriSEL);
        
        //現在的方法
        SEL nowSEL = @selector(addBtnClickCount:to:forEvent:);
        Method nowMethod = class_getInstanceMethod(selfClass, nowSEL);
        
        //給原來的方法添加實現，防止原來的方法沒有實現引起奔潰
        BOOL addSupC = class_addMethod(selfClass, oriSEL, method_getImplementation(nowMethod), method_getTypeEncoding(oriMethod));
        if (addSupC) {
            //添加成功，則用現在的方法實現代替原來的方法
            class_replaceMethod(selfClass, nowSEL, method_getImplementation(oriMethod), method_getTypeEncoding(oriMethod));
        }else{
            //添加失敗,證明原來的方法有實現，直接交換這兩個方法
            method_exchangeImplementations(oriMethod, nowMethod);
        }
    });
}

//現在的方法
-(void)addBtnClickCount:(SEL)action to:(id)target forEvent:(UIEvent *)event
{
    [[ZTools shareInstance] countClicks];
    [super sendAction:action to:target forEvent:event];
}

@end

#import <Foundation/Foundation.h>

@interface ZTools : NSObject

@property (nonatomic,assign) NSInteger count;

+(instancetype)shareInstance;

-(void)countClicks;

@end

#import "ZTools.h"

@implementation ZTools

static id _instance;

+(instancetype)shareInstance
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [[ZTools alloc] init];
    });
    return _instance;
}

-(void)countClicks
{
    _count += 1;
    NSLog(@"點擊次數:%ld",_count);
}

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(50, 150, 100, 50)];
    [btn setTitle:@"btn" forState:UIControlStateNormal];
    [btn addTarget:self action:@selector(btnClicked:) forControlEvents:UIControlEventTouchUpInside];
    [btn setBackgroundColor:[UIColor lightGrayColor]];
    [self.view addSubview:btn];
    
    UIButton *btn1 = [[UIButton alloc] initWithFrame:CGRectMake(50, 250, 100, 50)];
    [btn1 setTitle:@"btn1" forState:UIControlStateNormal];
    [btn1 addTarget:self action:@selector(btnClicked:) forControlEvents:UIControlEventTouchUpInside];
    [btn1 setBackgroundColor:[UIColor lightGrayColor]];
    [self.view addSubview:btn1];
}

-(void)btnClicked:(UIButton *)sender
{
    NSLog(@"btn clicked...");
}