iOS 消息处理之performSelector

Posted 2020-08-24 雨季的雾

//
//  RootViewController.h
//  DSCategories
//
//  Created by dasheng on 15/12/17.
//  Copyright ? 2015年 dasheng. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface RootViewController : UITableViewController

@end

 

//
//  RootViewController.m
//  DSCategories
//
//  Created by dasheng on 15/12/17.
//  Copyright ? 2015年 dasheng. All rights reserved.
//
//performSelector和直接调用方法的区别
//
//performSelector: withObject:是在ios中的一种方法调用方式。他可以向一个对象传递任何消息，而不需要在编译的时候声明这些方法。所以这也是runtime的一种应用方式。
//
//所以performSelector和直接调用方法的区别就在与runtime。直接调用编译是会自动校验。如果方法不存在，那么直接调用 在编译时候就能够发现，编译器会直接报错。
//但是使用performSelector的话一定是在运行时候才能发现，如果此方法不存在就会崩溃。所以如果使用performSelector的话他就会有个最佳伴侣- (BOOL)respondsToSelector:(SEL)aSelector;来在运行时判断对象是否响应此方法。

#import "RootViewController.h"
#import <objc/runtime.h>
#import <objc/message.h>

typedef struct ParameterStruct{
    int a;
    int b;
}MyStruct;

@interface RootViewController ()
{
    NSArray * _sectionAry;
    NSArray * _rowAry;
    NSArray * _selAry;
}

@end

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    self.title = @"Util";
    _sectionAry = @[@"PerformSelector的方法",
                    @"PerformSelector的方法延迟调用",
                    @"在子线程中无法调用selector方法"];
    
    _rowAry = @[ @[@"NoParameter",
                  @"OneParameter",
                  @"TwoParameter",
                  @"Dynamic Method",
                  @"NSInvocation",
                  @"objc_msgSend",
                  @"StructParameter",
                  @"StructParameter_Two"],
                @[@"InBackground",
                  @"onMainThread YES",
                  @"onMainThread NO",
                  @"simple",
                  @"simple delay"],
                @[@"No afterDelay",
                  @"AfterDelay",
                  @"AfterDelay Runloop",
                  @"dispatch_after"]];
    
    _selAry = @[ @[@"NoParameterClick",
                   @"OneParameterClick",
                   @"TwoParameterClick",
                   @"DynamicClick",
                   @"NSInvocationClick",
                   @"ObjcMsgSendClick",
                   @"StruckClick",
                   @"StruckTwoClick"],
                 @[@"inBackgroundClick",
                   @"onMainThreadWaitYesClick",
                   @"onMainThreadWaitNoClick",
                   @"simpleClick",
                   @"simpleDelayClick"],
                 @[@"NoAfterDelayClick",
                   @"AfterDelayClick",
                   @"AfterDelayRunloopClick",
                   @"dispatchAfterClick"]];
    [self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"Cell"];
    [self.tableView reloadData];
}

#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return _sectionAry.count;
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{
    return _sectionAry[section];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [_rowAry[section] count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
    // Configure the cell...
    cell.textLabel.text = _rowAry[indexPath.section][indexPath.row];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    return cell;
}

#pragma mark - Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    SEL sel = NSSelectorFromString(_selAry[indexPath.section][indexPath.row]);
    [self performSelector:sel];
}

#pragma mark - action method

#pragma 下面两种方法都可以用做传递多个参数用

//传递三个及以上的参数
- (id)performSelector:(SEL)selector withObjects:(NSArray *)objects
{
    // 方法签名(方法的描述)
    NSMethodSignature *signature = [[self class] instanceMethodSignatureForSelector:selector];
    if (signature == nil) {
        
        //可以抛出异常也可以不操作。
    }
    
    // NSInvocation : 利用一个NSInvocation对象包装一次方法调用（方法调用者、方法名、方法参数、方法返回值）
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
    invocation.target = self;
    invocation.selector = selector;
    
    // 设置参数
    NSInteger paramsCount = signature.numberOfArguments - 2; // 除self、_cmd以外的参数个数
    paramsCount = MIN(paramsCount, objects.count);
    for (NSInteger i = 0; i < paramsCount; i++) {
        id object = objects[i];
        if ([object isKindOfClass:[NSNull class]]) continue;
        [invocation setArgument:&object atIndex:i + 2];
    }
    
    // 调用方法
    [invocation invoke];
    
    // 获取返回值
    id returnValue = nil;
    if (signature.methodReturnLength) { // 有返回值类型，才去获得返回值
        [invocation getReturnValue:&returnValue];
    }
    
    return returnValue;
}

//在主线程上调用
- (void) performSelectorOnMainThread:(SEL)selector withObjects:(NSArray *)objects waitUntilDone:(BOOL)wait{
    
    NSMethodSignature *signature = [self methodSignatureForSelector:selector];
    if (!signature)
        return;
    NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:signature];
    [invocation setTarget:self];
    [invocation setSelector:selector];
    
    // 设置参数
    NSInteger paramsCount = signature.numberOfArguments - 2; // 除self、_cmd以外的参数个数
    paramsCount = MIN(paramsCount, objects.count);
    for (NSInteger i = 0; i < paramsCount; i++) {
        id object = objects[i];
        if ([object isKindOfClass:[NSNull class]]) continue;
        [invocation setArgument:&object atIndex:i + 2];
    }
    [invocation retainArguments];
    
    [invocation performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:wait];
}

#pragma  Click Method

//无参数
- (void)NoParameterClick {
    [self performSelector:@selector(SelectorNoParameter)];
}

//单参数
- (void)OneParameterClick {
    [self performSelector:@selector(SelectorOneParameter:) withObject:@"firstParameter"];
}

//双参数
- (void)TwoParameterClick {
    [self performSelector:@selector(SelectorFirstParameter:SecondParameter:) withObject:@"firstParameter" withObject:@"secondParameter"];
}

//动态添加函数
- (void)DynamicClick {
    NSArray *objectArray = @[@{@"methodName":@"DynamicParameterString:",@"value":@"String"},@{@"methodName":@"DynamicParameterNumber:",@"value":@2}];
    for (NSDictionary *dic in objectArray) {
        [self performSelector:NSSelectorFromString([dic objectForKey:@"methodName"]) withObject:[dic objectForKey:@"value"]];
    }
}

//传递三个及以上的参数
//第一种：NSInvocation
- (void)NSInvocationClick {
    NSString *str = @"字符串";
    NSNumber *num = @20;
    NSArray *arr = @[@"数组值1", @"数组值2"];
    SEL sel = NSSelectorFromString(@"NSInvocationWithString:withNum:withArray:");
    NSArray *objs = [NSArray arrayWithObjects:str, num, arr, nil];
    //[self performSelector:sel withObjects:objs];
    //在主线程上执行方法，阻塞主线程，直到主线程将代码块执行完毕
    [self performSelectorOnMainThread:sel withObjects:objs waitUntilDone:YES];
}

//第三种：objc_msgSend
- (void)ObjcMsgSendClick {
    NSString *str = @"字符串objc_msgSend";
    NSNumber *num = @20;
    NSArray *arr = @[@"数组值1", @"数组值2"];
    
    SEL sel = NSSelectorFromString(@"ObjcMsgSendWithString:withNum:withArray:");
    
    ((void (*) (id, SEL, NSString *, NSNumber *, NSArray *)) objc_msgSend) (self, sel, str, num, arr);
}

//传递多个参数，参数里面有结构体
- (void)StruckClick {
    NSString *str = @"字符串 结构体";
    NSNumber *num = @20;
    NSArray *arr = @[@"数组值1", @"数组值2"];
    MyStruct mystruct = {10,20};
    
    SEL sel = NSSelectorFromString(@"ObjcMsgSendWithString:withNum:withArray:withStruck:");
    
    ((void (*) (id, SEL, NSString *, NSNumber *, NSArray *, MyStruct)) objc_msgSend) (self, sel, str, num, arr, mystruct);
}

//参数中有结构体
- (void)StruckTwoClick {
    
    NSString *str = @"字符串 把结构体转换为对象";
    NSNumber *num = @20;
    NSArray *arr = @[@"数组值1", @"数组值2"];
    
    MyStruct mystruct = {10,20};
    NSValue *value = [NSValue valueWithBytes:&mystruct objCType:@encode(MyStruct)];
    
    SEL sel = NSSelectorFromString(@"NSInvocationWithString:withNum:withArray:withValue:");
    NSArray *objs = [NSArray arrayWithObjects:str, num, arr, value,nil];
    
    [self performSelector:sel withObjects:objs];
}

#pragma mark - Perform Selector method

- (void)SelectorNoParameter{
    
    NSLog(@"SelectorNoParameter");
}

- (void)SelectorOneParameter:(NSString *)first{
    
    NSLog(@"Logs: %@", first);
}

- (void)SelectorFirstParameter:(NSString *)first SecondParameter:(NSString *)second{
    
    NSLog(@"Logs %@ %@", first, second);
}

//动态添加函数
- (void)DynamicParameterString:(NSString *)string{
    
    NSLog(@"DynamicParameterString: %@",string);
}

- (void)DynamicParameterNumber:(NSNumber *)number{
    
    NSLog(@"DynamicParameterNumber: %@",number);
}

//多参数
- (void)NSInvocationWithString:(NSString *)string withNum:(NSNumber *)number withArray:(NSArray *)array {
    NSLog(@"%@, %@, %@", string, number, array[0]);
}

- (void)ObjcMsgSendWithString:(NSString *)string withNum:(NSNumber *)number withArray:(NSArray *)array {
    NSLog(@"%@, %@, %@", string, number, array[0]);
}

//多参数有struck
- (void)NSInvocationWithString:(NSString *)string withNum:(NSNumber *)number withArray:(NSArray *)array withValue:(NSValue *)value{
    
    MyStruct struceBack;
    [value getValue:&struceBack];
    
    NSLog(@"%@, %@, %@, %d", string, number, array[0],struceBack.a);
}

- (void)ObjcMsgSendWithString:(NSString *)string withNum:(NSNumber *)number withArray:(NSArray *)array withStruck:(MyStruct)mystruct{
    
    NSLog(@"%@, %@, %@, %d", string, number, array[0],mystruct.a);
}

#pragma mark - perform selector 方法延迟调用
//这个方法是直接在后台线程运行。
- (void)inBackgroundClick {
    [self performSelectorInBackground:@selector(delayMethod) withObject:nil];
    NSLog(@"调用方法＝＝开始");
    sleep(5);
    NSLog(@"调用方法＝＝结束");
}

//在主线程执行方法-参数wait如果为YES表示是否等待方法执行完毕再往下执行
- (void)onMainThreadWaitYesClick {
    [self performSelectorOnMainThread:@selector(delayMethod) withObject:nil waitUntilDone:YES];
    NSLog(@"调用方法＝＝开始");
    sleep(5);
    NSLog(@"调用方法＝＝结束");
}

//在主线程执行方法-参数wait为NO，还是跟原来使用afterDelay:(NSTimeInterval)delay方式一样，要等当前调用此方法的函数执行完毕后
- (void)onMainThreadWaitNoClick {
    [self performSelectorOnMainThread:@selector(delayMethod) withObject:nil waitUntilDone:NO];
    NSLog(@"调用方法＝＝开始");
    sleep(5);
    NSLog(@"调用方法＝＝结束");
}

//最简单的一种方式
- (void)simpleClick {
    [self performSelector:@selector(delayMethod) withObject:nil];
    NSLog(@"调用方法＝＝开始");
    sleep(5);
    NSLog(@"调用方法＝＝结束");
}

//使用延时方法呢，可以使用dispatch_after在子线程上执行
- (void)simpleDelayClick {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_global_queue(0, 0), ^{
        if ([self respondsToSelector:@selector(delayMethod)]) {
            [self performSelector:@selector(delayMethod) withObject:nil];
        }
    });
    NSLog(@"调用方法＝＝开始");
    sleep(5);
    NSLog(@"调用方法＝＝结束");
}

- (void)delayMethod {
    NSLog(@"执行selector方法");
}

#pragma mark - @"在子线程中无法调用selector方法"
//在子线程中无法调用selector方法
//
//在子线程中无法调用selector方法这种情况是只有使用以下方法的时候才出现:
//
//- (void)performSelector:(SEL)aSelector withObject:(id)arg afterDelay:(NSTimeInterval)delay;
//

- (void)NoAfterDelayClick {
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        [self performSelector:@selector(delayMethodLater) withObject:nil];
        NSLog(@"调用方法＝＝开始");
        sleep(5);
        NSLog(@"调用方法＝＝结束");
    });
}


- (void)AfterDelayClick {
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        [self performSelector:@selector(delayMethodLater) withObject:nil afterDelay:0];
        NSLog(@"调用方法＝＝开始");
        sleep(5);
        NSLog(@"调用方法＝＝结束");
    });
}

//这是为什么呢？原因如下：
//
//1、afterDelay方式是使用当前线程的Run Loop中根据afterDelay参数创建一个Timer定时器在一定时间后调用SEL，NO AfterDelay方式是直接调用SEL。
//
//2、子线程中默认是没有runloop的，需要手动创建，只要调用获取当前线程RunLoop方法即可创建。
//
//所以解决方法有两种：
//
//创建子线程的runloop
- (void)AfterDelayRunloopClick {
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        [self performSelector:@selector(delayMethodLater) withObject:nil afterDelay:0];
        [[NSRunLoop currentRunLoop] run];
        NSLog(@"调用方法＝＝开始");
        sleep(5);
        NSLog(@"调用方法＝＝结束");
    });
}

//使用dispatch_after在子线程上执行
- (void)dispatchAfterClick {
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_global_queue(0, 0), ^{
            if ([self respondsToSelector:@selector(delayMethodLater)]) {
                [self performSelector:@selector(delayMethodLater) withObject:nil];
            }
        });
        NSLog(@"调用方法＝＝开始");
        sleep(5);
        NSLog(@"调用方法＝＝结束");
    });
}

- (void)delayMethodLater {
    NSLog(@"执行延迟方法");
}

@end