iOS开发runtime的使用场景

1、Method Swizzling（动态方法交换）
Method Swizzling用于改变一个已存在的selector实现。我们可以在程序运行时，通过改变selector所在Class（类）的method list（方法列表）的映射从而改变方法的调用。其实质就是交换两个方法的IMP（方法实现）。

2、Method Swizzling应用场景
2.1、全局页面统计功能

#import "UIViewController+Swizzling.h"
#import <objc/runtime.h>

@implementation UIViewController (Swizzling)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];
        
        SEL originalSelector = @selector(viewWillAppear:);
        SEL swizzledSelector = @selector(xxx_viewWillAppear:);
        
        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
        
        BOOL didAddMethod = class_addMethod(class,
                                            originalSelector,
                                            method_getImplementation(swizzledMethod),
                                            method_getTypeEncoding(swizzledMethod));
        
        if (didAddMethod) {
            class_replaceMethod(class,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

#pragma mark - Method Swizzling

- (void)xxx_viewWillAppear:(BOOL)animated {
    
    if (![self isKindOfClass:[UIViewController class]]) {  // 剔除系统 UIViewController
        // 添加统计代码
        NSLog(@"进入页面：%@", [self class]);
    }
    
    [self xxx_viewWillAppear:animated];
}

@end

2.2字体根据屏幕尺寸适配

#import "UIFont+AdjustSwizzling.h"
#import <objc/runtime.h>

#define XXX_UISCREEN_WIDTH  375

@implementation UIFont (AdjustSwizzling)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];

        SEL originalSelector = @selector(systemFontOfSize:);
        SEL swizzledSelector = @selector(xxx_systemFontOfSize:);

        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

        BOOL didAddMethod = class_addMethod(class,
                                            originalSelector,
                                            method_getImplementation(swizzledMethod),
                                            method_getTypeEncoding(swizzledMethod));

        if (didAddMethod) {
            class_replaceMethod(class,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

+ (UIFont *)xxx_systemFontOfSize:(CGFloat)fontSize {
    UIFont *newFont = nil;
    newFont = [UIFont xxx_systemFontOfSize:fontSize * [UIScreen mainScreen].bounds.size.width / XXX_UISCREEN_WIDTH];
    
    return newFont;
}

@end

2.3处理按钮重复点击

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

@interface UIButton()

// 重复点击间隔
@property (nonatomic, assign) NSTimeInterval xxx_acceptEventInterval;

@end


@implementation UIButton (DelaySwizzling)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];

        SEL originalSelector = @selector(sendAction:to:forEvent:);
        SEL swizzledSelector = @selector(xxx_sendAction:to:forEvent:);

        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

        BOOL didAddMethod = class_addMethod(class,
                                            originalSelector,
                                            method_getImplementation(swizzledMethod),
                                            method_getTypeEncoding(swizzledMethod));

        if (didAddMethod) {
            class_replaceMethod(class,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

- (void)xxx_sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event {
    
    // 如果想要设置统一的间隔时间，可以在此处加上以下几句
    if (self.xxx_acceptEventInterval <= 0) {
        // 如果没有自定义时间间隔，则默认为 0.4 秒
        self.xxx_acceptEventInterval = 0.4;
    }
    
    // 是否小于设定的时间间隔
    BOOL needSendAction = (NSDate.date.timeIntervalSince1970 - self.xxx_acceptEventTime >= self.xxx_acceptEventInterval);
    
    // 更新上一次点击时间戳
    if (self.xxx_acceptEventInterval > 0) {
        self.xxx_acceptEventTime = NSDate.date.timeIntervalSince1970;
    }
    
    // 两次点击的时间间隔小于设定的时间间隔时，才执行响应事件
    if (needSendAction) {
        [self xxx_sendAction:action to:target forEvent:event];
    }
}

- (NSTimeInterval )xxx_acceptEventInterval{
    return [objc_getAssociatedObject(self, "UIControl_acceptEventInterval") doubleValue];
}

- (void)setXxx_acceptEventInterval:(NSTimeInterval)xxx_acceptEventInterval{
    objc_setAssociatedObject(self, "UIControl_acceptEventInterval", @(xxx_acceptEventInterval), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSTimeInterval )xxx_acceptEventTime{
    return [objc_getAssociatedObject(self, "UIControl_acceptEventTime") doubleValue];
}

- (void)setXxx_acceptEventTime:(NSTimeInterval)xxx_acceptEventTime{
    objc_setAssociatedObject(self, "UIControl_acceptEventTime", @(xxx_acceptEventTime), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end

2.4、TableView、CollectionView异常加载占位图

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UITableView (ReloadDataSwizzling)

@property (nonatomic, assign) BOOL firstReload;
@property (nonatomic, strong) UIView *placeholderView;
@property (nonatomic,   copy) void(^reloadBlock)(void);

@end

/*--------------------------------------*/

#import "UITableView+ReloadDataSwizzling.h"
#import "XXXPlaceholderView.h"
#import <objc/runtime.h>

@implementation UITableView (ReloadDataSwizzling)


+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];

        SEL originalSelector = @selector(reloadData);
        SEL swizzledSelector = @selector(xxx_reloadData);

        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

        BOOL didAddMethod = class_addMethod(class,
                                            originalSelector,
                                            method_getImplementation(swizzledMethod),
                                            method_getTypeEncoding(swizzledMethod));

        if (didAddMethod) {
            class_replaceMethod(class,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

- (void)xxx_reloadData {
    if (!self.firstReload) {
        [self checkEmpty];
    }
    self.firstReload = NO;
    
    [self xxx_reloadData];
}


- (void)checkEmpty {
    BOOL isEmpty = YES; // 判空 flag 标示
    
    id <UITableViewDataSource> dataSource = self.dataSource;
    NSInteger sections = 1; // 默认TableView 只有一组
    if ([dataSource respondsToSelector:@selector(numberOfSectionsInTableView:)]) {
        sections = [dataSource numberOfSectionsInTableView:self] - 1; // 获取当前TableView 组数
    }
    
    for (NSInteger i = 0; i <= sections; i++) {
        NSInteger rows = [dataSource tableView:self numberOfRowsInSection:i]; // 获取当前TableView各组行数
        if (rows) {
            isEmpty = NO; // 若行数存在，不为空
        }
    }
    if (isEmpty) { // 若为空，加载占位图
        if (!self.placeholderView) { // 若未自定义，加载默认占位图
            [self makeDefaultPlaceholderView];
        }
        self.placeholderView.hidden = NO;
        [self addSubview:self.placeholderView];
    } else { // 不为空，隐藏占位图
        self.placeholderView.hidden = YES;
    }
}

- (void)makeDefaultPlaceholderView {
    self.bounds = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
    XXXPlaceholderView *placeholderView = [[XXXPlaceholderView alloc] initWithFrame:self.bounds];
    __weak typeof(self) weakSelf = self;
    [placeholderView setReloadClickBlock:^{
        if (weakSelf.reloadBlock) {
            weakSelf.reloadBlock();
        }
    }];
    self.placeholderView = placeholderView;
}

- (BOOL)firstReload {
    return [objc_getAssociatedObject(self, @selector(firstReload)) boolValue];
}

- (void)setFirstReload:(BOOL)firstReload {
    objc_setAssociatedObject(self, @selector(firstReload), @(firstReload), OBJC_ASSOCIATION_ASSIGN);
}

- (UIView *)placeholderView {
    return objc_getAssociatedObject(self, @selector(placeholderView));
}

- (void)setPlaceholderView:(UIView *)placeholderView {
    objc_setAssociatedObject(self, @selector(placeholderView), placeholderView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (void (^)(void))reloadBlock {
    return objc_getAssociatedObject(self, @selector(reloadBlock));
}

- (void)setReloadBlock:(void (^)(void))reloadBlock {
    objc_setAssociatedObject(self, @selector(reloadBlock), reloadBlock, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

@end

2.5、数组，字典赋值重写拦截防止nil奔溃
dic

#import "NSDictionary+Safe.h"
#import <objc/runtime.h>
 
@implementation NSDictionary (Safe)
 
+ (void)load {
    Method originalMethod = class_getClassMethod(self, @selector(dictionaryWithObjects:forKeys:count:));
    Method swizzledMethod = class_getClassMethod(self, @selector(na_dictionaryWithObjects:forKeys:count:));
    method_exchangeImplementations(originalMethod, swizzledMethod);
}
 
+ (instancetype)na_dictionaryWithObjects:(const id [])objects forKeys:(const id <NSCopying> [])keys count:(NSUInteger)cnt {
    id nObjects[cnt];
    id nKeys[cnt];
    int i=0, j=0;
    for (; i<cnt && j<cnt; i++) {
        if (objects[i] && keys[i]) {
            nObjects[j] = objects[i];
            nKeys[j] = keys[i];
            j++;
        }
    }
    
    return [self na_dictionaryWithObjects:nObjects forKeys:nKeys count:j];
}
 
@end
 
@implementation NSMutableDictionary (Safe)
 
+ (void)load {
    Class dictCls = NSClassFromString(@"__NSDictionaryM");
    Method originalMethod = class_getInstanceMethod(dictCls, @selector(setObject:forKey:));
    Method swizzledMethod = class_getInstanceMethod(dictCls, @selector(na_setObject:forKey:));
    method_exchangeImplementations(originalMethod, swizzledMethod);
}
 
- (void)na_setObject:(id)anObject forKey:(id<NSCopying>)aKey {
    if (!anObject || !aKey)
        return;
    [self na_setObject:anObject forKey:aKey];
}
 
@end

array

#import "NSArray+Safe.h"
#import <objc/runtime.h>
 
@implementation NSArray (Safe)
 
+ (void)load {
    Method originalMethod = class_getClassMethod(self, @selector(arrayWithObjects:count:));
    Method swizzledMethod = class_getClassMethod(self, @selector(na_arrayWithObjects:count:));
    method_exchangeImplementations(originalMethod, swizzledMethod);
}
 
+ (instancetype)na_arrayWithObjects:(const id [])objects count:(NSUInteger)cnt {
    id nObjects[cnt];
    int i=0, j=0;
    for (; i<cnt && j<cnt; i++) {
        if (objects[i]) {
            nObjects[j] = objects[i];
            j++;
        }
    }
    
    return [self na_arrayWithObjects:nObjects count:j];
}
@end
 
@implementation NSMutableArray (Safe)
 
+ (void)load {
    Class arrayCls = NSClassFromString(@"__NSArrayM");
    
    Method originalMethod1 = class_getInstanceMethod(arrayCls, @selector(insertObject:atIndex:));
    Method swizzledMethod1 = class_getInstanceMethod(arrayCls, @selector(na_insertObject:atIndex:));
    method_exchangeImplementations(originalMethod1, swizzledMethod1);
    
    Method originalMethod2 = class_getInstanceMethod(arrayCls, @selector(setObject:atIndex:));
    Method swizzledMethod2 = class_getInstanceMethod(arrayCls, @selector(na_setObject:atIndex:));
    method_exchangeImplementations(originalMethod2, swizzledMethod2);
}
 
- (void)na_insertObject:(id)anObject atIndex:(NSUInteger)index {
    if (!anObject)
        return;
    [self na_insertObject:anObject atIndex:index];
}
 
- (void)na_setObject:(id)anObject atIndex:(NSUInteger)index {
    if (!anObject)
        return;
    [self na_setObject:anObject atIndex:index];
}
 
@end

3、修改私有属性
3.1、更改UITextField占位文字的颜色和字号

// 打印 UITextfield 的所有属性和成员变量
- (void)printUITextFieldList {
    unsigned int count;
    
    Ivar *ivarList = class_copyIvarList([UITextField class], &count);
    for (unsigned int i = 0; i < count; i++) {
        Ivar myIvar = ivarList[i];
        const char *ivarName = ivar_getName(myIvar);
        NSLog(@"ivar(%d) : %@", i, [NSString stringWithUTF8String:ivarName]);
    }
    
    free(ivarList);
    
    objc_property_t *propertyList = class_copyPropertyList([UITextField class], &count);
    for (unsigned int i = 0; i < count; i++) {
        const char *propertyName = property_getName(propertyList[i]);
        NSLog(@"propertyName(%d) : %@", i, [NSString stringWithUTF8String:propertyName]);
    }
    
    free(propertyList);
}

// 通过修改 UITextfield 的私有属性更改占位颜色和字体
- (void)createLoginTextField {
    UITextField *loginTextField = [[UITextField alloc] init];
    loginTextField.frame = CGRectMake(15,(self.view.bounds.size.height-52-50)/2, self.view.bounds.size.width-60-18,52);
    loginTextField.delegate = self;
    loginTextField.font = [UIFont systemFontOfSize:14];
    loginTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
    loginTextField.textColor = [UIColor blackColor];
    
    loginTextField.placeholder = @"用户名/邮箱";
    [loginTextField setValue:[UIFont systemFontOfSize:15] forKeyPath:@"_placeholderLabel.font"];
    [loginTextField setValue:[UIColor lightGrayColor]forKeyPath:@"_placeholderLabel.textColor"];
    
    [self.view addSubview:loginTextField];
}

3.2、万能控制器跳转

// 定义的规则
NSDictionary *params = @{
                         @"class" : @"XXViewController",
                         @"property" : @{
                                 @"ID" : @"123",
                                 @"type" : @"XXViewController1"
                                 }
                         };

然后，添加一个工具类 XXJumpControllerTool，添加跳转相关的类方法。

/********************* XXJumpControllerTool.h 文件 *********************/

#import <Foundation/Foundation.h>

@interface XXJumpControllerTool : NSObject

+ (void)pushViewControllerWithParams:(NSDictionary *)params;

@end


/********************* XXJumpControllerTool.m 文件 *********************/

#import "XXJumpControllerTool.h"
#import <UIKit/UIKit.h>
#import <objc/runtime.h>

@implementation XXJumpControllerTool

+ (void)pushViewControllerWithParams:(NSDictionary *)params {
    // 取出控制器类名
    NSString *classNameStr = [NSString stringWithFormat:@"%@", params[@"class"]];
    const char *className = [classNameStr cStringUsingEncoding:NSASCIIStringEncoding];
    
    // 根据字符串返回一个类
    Class newClass = objc_getClass(className);
    if (!newClass) {
        // 创建一个类
        Class superClass = [NSObject class];
        newClass = objc_allocateClassPair(superClass, className, 0);
        // 注册你创建的这个类
        objc_registerClassPair(newClass);
    }

    // 创建对象（就是控制器对象）
    id instance = [[newClass alloc] init];
    
    NSDictionary *propertys = params[@"property"];
    [propertys enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        // 检测这个对象是否存在该属性
        if ([XXJumpControllerTool checkIsExistPropertyWithInstance:instance verifyPropertyName:key]) {
            // 利用 KVC 对控制器对象的属性赋值
            [instance setValue:obj forKey:key];
        }
    }];
    
    
    // 跳转到对应的控制器
    [[XXJumpControllerTool topViewController].navigationController pushViewController:instance animated:YES];
}


// 检测对象是否存在该属性
+ (BOOL)checkIsExistPropertyWithInstance:(id)instance verifyPropertyName:(NSString *)verifyPropertyName {
    unsigned int count, i;
    
    // 获取对象里的属性列表
    objc_property_t *properties = class_copyPropertyList([instance class], &count);
    
    for (i = 0; i < count; i++) {
        objc_property_t property =properties[i];
        //  属性名转成字符串
        NSString *propertyName = [[NSString alloc] initWithCString:property_getName(property) encoding:NSUTF8StringEncoding];
        // 判断该属性是否存在
        if ([propertyName isEqualToString:verifyPropertyName]) {
            free(properties);
            return YES;
        }
    }
    free(properties);
    
    return NO;
}

// 获取当前显示在屏幕最顶层的 ViewController
+ (UIViewController *)topViewController {
    UIViewController *resultVC = [XXJumpControllerTool _topViewController:[[UIApplication sharedApplication].keyWindow rootViewController]];
    while (resultVC.presentedViewController) {
        resultVC = [XXJumpControllerTool _topViewController:resultVC.presentedViewController];
    }
    return resultVC;
}

+ (UIViewController *)_topViewController:(UIViewController *)vc {
    if ([vc isKindOfClass:[UINavigationController class]]) {
        return [XXJumpControllerTool _topViewController:[(UINavigationController *)vc topViewController]];
    } else if ([vc isKindOfClass:[UITabBarController class]]) {
        return [XXJumpControllerTool _topViewController:[(UITabBarController *)vc selectedViewController]];
    } else {
        return vc;
    }
    return nil;
}

@end

3.3改进iOS归档和解档

// 解档
- (instancetype)xx_modelInitWithCoder:(NSCoder *)aDecoder {
    if (!aDecoder) return self;
    if (!self) {
        return self;
    }
    
    unsigned int count;
    objc_property_t *propertyList = class_copyPropertyList([self class], &count);
    for (unsigned int i = 0; i < count; i++) {
        const char *propertyName = property_getName(propertyList[i]);
        NSString *name = [NSString stringWithUTF8String:propertyName];
        
        id value = [aDecoder decodeObjectForKey:name];
        [self setValue:value forKey:name];
    }
    free(propertyList);
    
    return self;
}

// 归档
- (void)xx_modelEncodeWithCoder:(NSCoder *)aCoder {
    if (!aCoder) return;
    if (!self) {
        return;
    }
    unsigned int count;
    objc_property_t *propertyList = class_copyPropertyList([self class], &count);
    for (unsigned int i = 0; i < count; i++) {
        const char *propertyName = property_getName(propertyList[i]);
        NSString *name = [NSString stringWithUTF8String:propertyName];
        
        id value = [self valueForKey:name];
        [aCoder encodeObject:value forKey:name];
    }
    free(propertyList);
}

然后在需要实现归档解档的模型中，添加 -initWithCoder: 和 -encodeWithCoder: 方法。

#import "XXPerson.h"
#import "NSObject+XXModel.h"

@implementation XXPerson

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super init];
    if (self) {
        [self xx_modelInitWithCoder:aDecoder];
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {
    [self xx_modelEncodeWithCoder:aCoder];
}

@end

3.4、按钮的重复点击

+ (void)load{
    Method originalMethod = class_getInstanceMethod([self class], @selector(sendAction:to:forEvent:));
    Method swizzledMethod = class_getInstanceMethod([self class], @selector(User_SendAction:to:forEvent:));
    method_exchangeImplementations(originalMethod, swizzledMethod);
}
 
#pragma mark -- 时间间隔 --
static const void *ButtonDurationTime = @"ButtonDurationTime";
- (NSTimeInterval)durationTime{
    NSNumber *number = objc_getAssociatedObject(self, &ButtonDurationTime);
    return number.doubleValue;
}
- (void)setDurationTime:(NSTimeInterval)durationTime{
    NSNumber *number = [NSNumber numberWithDouble:durationTime];
    objc_setAssociatedObject(self, &ButtonDurationTime, number, OBJC_ASSOCIATION_COPY_NONATOMIC);
   
}
 
- (void)User_SendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event{
  
    self.userInteractionEnabled = NO;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(self.durationTime * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        self.userInteractionEnabled = YES;
    });
    
    [self User_SendAction:action to:target forEvent:event];
}

3.5、字典转模型