iOS 消息處理之performSelector

//
//  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和直接調用方法的區別
//
//performSelector: withObject:是在iOS中的一種方法調用方式。他可以向一個對象傳遞任何消息，而不需要在編譯的時候聲明這些方法。所以這也是runtime的一種應用方式。
//
//所以performSelector和直接調用方法的區別就在與runtime。直接調用編譯是會自動校驗。如果方法不存在，那么直接調用 在編譯時候就能夠發現，編譯器會直接報錯。
//但是使用performSelector的話一定是在運行時候才能發現，如果此方法不存在就會崩潰。所以如果使用performSelector的話他就會有個最佳伴侶- (BOOL)respondsToSelector:(SEL)aSelector;來在運行時判斷對象是否響應此方法。

#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的方法延遲調用",
                    @"在子線程中無法調用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 下面兩種方法都可以用做傳遞多個參數用

//傳遞三個及以上的參數
- (id)performSelector:(SEL)selector withObjects:(NSArray *)objects
{
    // 方法簽名(方法的描述)
    NSMethodSignature *signature = [[self class] instanceMethodSignatureForSelector:selector];
    if (signature == nil) {
        
        //可以拋出異常也可以不操作。
    }
    
    // NSInvocation : 利用一個NSInvocation對象包裝一次方法調用（方法調用者、方法名、方法參數、方法返回值）
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
    invocation.target = self;
    invocation.selector = selector;
    
    // 設置參數
    NSInteger paramsCount = signature.numberOfArguments - 2; // 除self、_cmd以外的參數個數
    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];
    }
    
    // 調用方法
    [invocation invoke];
    
    // 獲取返回值
    id returnValue = nil;
    if (signature.methodReturnLength) { // 有返回值類型，才去獲得返回值
        [invocation getReturnValue:&returnValue];
    }
    
    return returnValue;
}

//在主線程上調用
- (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];
    
    // 設置參數
    NSInteger paramsCount = signature.numberOfArguments - 2; // 除self、_cmd以外的參數個數
    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

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

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

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

//動態添加函數
- (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"]];
    }
}

//傳遞三個及以上的參數
//第一種：NSInvocation
- (void)NSInvocationClick {
    NSString *str = @"字符串";
    NSNumber *num = @20;
    NSArray *arr = @[@"數組值1", @"數組值2"];
    SEL sel = NSSelectorFromString(@"NSInvocationWithString:withNum:withArray:");
    NSArray *objs = [NSArray arrayWithObjects:str, num, arr, nil];
    //[self performSelector:sel withObjects:objs];
    //在主線程上執行方法，阻塞主線程，直到主線程將代碼塊執行完畢
    [self performSelectorOnMainThread:sel withObjects:objs waitUntilDone:YES];
}

//第三種：objc_msgSend
- (void)ObjcMsgSendClick {
    NSString *str = @"字符串objc_msgSend";
    NSNumber *num = @20;
    NSArray *arr = @[@"數組值1", @"數組值2"];
    
    SEL sel = NSSelectorFromString(@"ObjcMsgSendWithString:withNum:withArray:");
    
    ((void (*) (id, SEL, NSString *, NSNumber *, NSArray *)) objc_msgSend) (self, sel, str, num, arr);
}

//傳遞多個參數，參數里面有結構體
- (void)StruckClick {
    NSString *str = @"字符串 結構體";
    NSNumber *num = @20;
    NSArray *arr = @[@"數組值1", @"數組值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);
}

//參數中有結構體
- (void)StruckTwoClick {
    
    NSString *str = @"字符串 把結構體轉換為對象";
    NSNumber *num = @20;
    NSArray *arr = @[@"數組值1", @"數組值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);
}

//動態添加函數
- (void)DynamicParameterString:(NSString *)string{
    
    NSLog(@"DynamicParameterString: %@",string);
}

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

//多參數
- (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]);
}

//多參數有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 方法延遲調用
//這個方法是直接在后台線程運行。
- (void)inBackgroundClick {
    [self performSelectorInBackground:@selector(delayMethod) withObject:nil];
    NSLog(@"調用方法＝＝開始");
    sleep(5);
    NSLog(@"調用方法＝＝結束");
}

//在主線程執行方法-參數wait如果為YES表示是否等待方法執行完畢再往下執行
- (void)onMainThreadWaitYesClick {
    [self performSelectorOnMainThread:@selector(delayMethod) withObject:nil waitUntilDone:YES];
    NSLog(@"調用方法＝＝開始");
    sleep(5);
    NSLog(@"調用方法＝＝結束");
}

//在主線程執行方法-參數wait為NO，還是跟原來使用afterDelay:(NSTimeInterval)delay方式一樣，要等當前調用此方法的函數執行完畢后
- (void)onMainThreadWaitNoClick {
    [self performSelectorOnMainThread:@selector(delayMethod) withObject:nil waitUntilDone:NO];
    NSLog(@"調用方法＝＝開始");
    sleep(5);
    NSLog(@"調用方法＝＝結束");
}

//最簡單的一種方式
- (void)simpleClick {
    [self performSelector:@selector(delayMethod) withObject:nil];
    NSLog(@"調用方法＝＝開始");
    sleep(5);
    NSLog(@"調用方法＝＝結束");
}

//使用延時方法呢，可以使用dispatch_after在子線程上執行
- (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(@"調用方法＝＝開始");
    sleep(5);
    NSLog(@"調用方法＝＝結束");
}

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

#pragma mark - @"在子線程中無法調用selector方法"
//在子線程中無法調用selector方法
//
//在子線程中無法調用selector方法這種情況是只有使用以下方法的時候才出現:
//
//- (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(@"調用方法＝＝開始");
        sleep(5);
        NSLog(@"調用方法＝＝結束");
    });
}


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

//這是為什么呢？原因如下：
//
//1、afterDelay方式是使用當前線程的Run Loop中根據afterDelay參數創建一個Timer定時器在一定時間后調用SEL，NO AfterDelay方式是直接調用SEL。
//
//2、子線程中默認是沒有runloop的，需要手動創建，只要調用獲取當前線程RunLoop方法即可創建。
//
//所以解決方法有兩種：
//
//創建子線程的runloop
- (void)AfterDelayRunloopClick {
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        [self performSelector:@selector(delayMethodLater) withObject:nil afterDelay:0];
        [[NSRunLoop currentRunLoop] run];
        NSLog(@"調用方法＝＝開始");
        sleep(5);
        NSLog(@"調用方法＝＝結束");
    });
}

//使用dispatch_after在子線程上執行
- (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(@"調用方法＝＝開始");
        sleep(5);
        NSLog(@"調用方法＝＝結束");
    });
}

- (void)delayMethodLater {
    NSLog(@"執行延遲方法");
}

@end