iOS 关于页面回调传值的总结（delegete、block）

应用方式为:

控制器A中有一个按钮，点击跳转至控制器B，控制器B中有多个按钮，点击不同的按钮，返回给A不同的内容。

1.block方式

A.m

#import "ViewControllerA.h"
#import "ViewControllerB.h"

@interface ViewControllerA ()

@property (nonatomic, strong) ViewControllerB *controllerB;

@property (nonatomic, strong) UILabel *testLabel;

@end

@implementation ViewControllerA

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
self.view.backgroundColor = [UIColor whiteColor];

UIButton *jumpButton = [[UIButton alloc] initWithFrame:CGRectMake(20, 80, 100, 100)];
jumpButton.backgroundColor = [UIColor redColor];
jumpButton.layer.cornerRadius = 50;
[jumpButton addTarget:self action:@selector(jumpButtonClickAction) forControlEvents:UIControlEventTouchUpInside];
[jumpButton setTitle:@"ToB" forState:UIControlStateNormal];
[self.view addSubview:jumpButton];

_testLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width - 40, 40)];
_testLabel.center = self.view.center;
_testLabel.textAlignment = NSTextAlignmentCenter;
_testLabel.backgroundColor = [UIColor lightGrayColor];
_testLabel.textColor = [UIColor redColor];
[self.view addSubview:_testLabel];
}

- (void)jumpButtonClickAction {

//TODO: 声明weakSelf 在Block中使用 方式Block循环引用
__weak typeof(self) weakSelf = self;
_controllerB = [[ViewControllerB alloc] init];

//TODO: 控制器中点击测试按钮 通过Block的回调实现
_controllerB.change_controllerA_labelTitleBlock = ^(NSString *title) {
weakSelf.testLabel.text = [NSString stringWithFormat:@"点击了%@",title];
};

[self.navigationController pushViewController:_controllerB animated:YES];
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end

B.h
#import <UIKit/UIKit.h>

@interface ViewControllerB : UIViewController

//TODO: 声明用来回调的 Block
@property (nonatomic, copy) void(^change_controllerA_labelTitleBlock)(NSString *title);

@end

B.m
#import "ViewControllerB.h"

@interface ViewControllerB ()

@end

@implementation ViewControllerB

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
self.view.backgroundColor = [UIColor whiteColor];

UIButton *buttonLeft = [[UIButton alloc] initWithFrame:CGRectMake(40, 100, 100, 100)];
buttonLeft.backgroundColor = [UIColor blackColor];
[buttonLeft setTitle:@"buttonLeft" forState:UIControlStateNormal];
[buttonLeft addTarget:self action:@selector(buttonClickAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:buttonLeft];

UIButton *buttonRight = [[UIButton alloc] initWithFrame:CGRectMake(CGRectGetMaxX(buttonLeft.frame) + 40, 100, 100, 100)];
buttonRight.backgroundColor = [UIColor blackColor];
[buttonRight setTitle:@"buttonRight" forState:UIControlStateNormal];
[buttonRight addTarget:self action:@selector(buttonClickAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:buttonRight];

}

- (void)buttonClickAction:(UIButton *)sender {

//TODO: 判断 self.change_controllerA_labelTitleBlock 是否为空（必写）
if (self.change_controllerA_labelTitleBlock) {

//TODO: Block 会调给控制器A 值
self.change_controllerA_labelTitleBlock(sender.titleLabel.text);
}
[self.navigationController popViewControllerAnimated:YES];
}

//TODO: Block Set方法(必写)
- (void)setChange_controllerA_labelTitleBlock:(void (^)(NSString *))change_controllerA_labelTitleBlock {
_change_controllerA_labelTitleBlock = change_controllerA_labelTitleBlock;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end

2.delegate

A.h

#import <UIKit/UIKit.h>
#import "ViewControllerB.h"

@interface ViewController : UIViewController <ViewControllerBDelegate>

@end

A.m

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *label;

@end

@implementation ViewController

//跳转按钮事件
- (IBAction)buttonAction:(UIButton *)sender {

ViewControllerB *vcB = [[ViewControllerB alloc] init];

//设置vcB的代理
vcB.delegate = self;

//跳转到vcB
[self.navigationController pushViewController:vcB animated:YES];

}
//实现协议方法
- (void)sendValue:(NSString *)string {

_label.text = string;

}

@end

B.h

#import <UIKit/UIKit.h>

@protocol ViewControllerBDelegate <NSObject>

- (void)sendValue:(NSString *)string;

@end

@interface ViewControllerB : UIViewController

// 委托代理，代理一般需使用弱引用(weak)
@property(nonatomic, weak) id<ViewControllerBDelegate>delegate;

@end

B.m

#import "ViewControllerB.h"

@interface ViewControllerB ()
@property (weak, nonatomic) IBOutlet UITextField *textField;

@end

@implementation ViewControllerB

//back按钮点击事件
- (IBAction)buttonAction:(UIButton *)sender {

//调用代理方法
[_delegate sendValue:_textField.text];
//跳转回vcA
[self.navigationController popToRootViewControllerAnimated:YES];

}

@end