iOS 学会使用delegate和block<二>
继上篇我们聊的delegate后，这节我们一块聊聊这个block，在开发中block我用到了两种情况，要不就是通过block来传值，要不就是通过block来传事件，下边我讲分两部分来讲block的传值和block的传事件。
block重命名，typedef
//typedef <#returnType#>(^<#name#>)(<#arguments#>);
typedef void(^callbackBlock)(NSString *tempStr,NSString *tempStr2,NSInteger count);
typedef NSString *(^callBlock)(NSString *str1,NSString *str2,NSString *str3);
由上边我们可以看出
返回值类型 block名字 传入的参数（可以是一个，可以是多个，可以没有）
第一：block传值
block传值在我理解来就是比如说是两个界面，界面之间的传值，一个界面的值生成后，通过block保存起来，然后，block里边就有第一个界面的值了，有了第一个值之后，通过block把值传到第二个界面，当然了这样说可能更容易理解点，其实不是这样的，真正的应该是在block代码块中的代码是不会执行的直至调用block的时候，block中的代码块才会被执行，给一个demo，他要实现的就是第二个界面的textField中的内容传给第一个界面的label上，demo如下：
viewCOntroller.h中
#import <UIKit/UIKit.h>
@interface ViewController :UIViewController
@property (nonatomic,strong)UIButton *clickButton;
@property (nonatomic,strong)UILabel *showLabel;
@end
viewController.m中
#import "ViewController.h"
#import "pushViewController.h"
@interfaceViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[superviewDidLoad];
// Do any additional setup after loading the view.
self.view.backgroundColor = [UIColorbrownColor];
self.clickButton = [UIButtonbuttonWithType:UIButtonTypeSystem];
self.clickButton.frame =CGRectMake(10,200,50, 50);
[self.clickButtonaddTarget:selfaction:@selector(click:)forControlEvents:UIControlEventTouchUpInside];
self.clickButton.backgroundColor = [UIColorredColor];
[self.viewaddSubview:self.clickButton];
self.showLabel = [[UILabelalloc]initWithFrame:CGRectMake(10,100,100, 50)];
self.showLabel.backgroundColor = [UIColoryellowColor];
[self.viewaddSubview:self.showLabel];
}
- (void)click:(UIButton *)sender {
NSLog(@"********");
pushViewController *push = [[pushViewControlleralloc]init];
push.block = ^(NSString *str) {
self.showLabel.text = str;
};
[self.navigationControllerpushViewController:pushanimated:YES];
}
@end
#import <UIKit/UIKit.h>
typedefvoid (^ blockPush)(NSString *textFieldStr);
@interface pushViewController :UIViewController
@property (nonatomic,copy)blockPush block;
@property (nonatomic,strong)UITextField *textField;
@end
pushViewController.m中
#import "pushViewController.h"
@interfacepushViewController ()
@end
@implementation pushViewController
- (void)viewDidLoad {
[superviewDidLoad];
self.textField = [[UITextFieldalloc]init];
self.textField.frame =CGRectMake(50,200,200,50);
self.textField.placeholder =@"place input word";
self.view.backgroundColor = [UIColorcolorWithRed:0.6green:0.6blue:0.2alpha:1];
self.textField.clipsToBounds =YES;
self.textField.borderStyle =UITextBorderStyleLine;
[self.viewaddSubview:self.textField];
UIBarButtonItem *backItem = [[UIBarButtonItemalloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAddtarget:selfaction:@selector(backClick:)];
self.navigationItem.leftBarButtonItem = backItem;
}
- (void)backClick:(UIBarButtonItem *)sender {
if (self.block) {
self.block(self.textField.text);
}
[self.navigationControllerpopViewControllerAnimated:YES];
}
@end
第二：block传事件
还是那个实现，我们这次用block来实现，demo如下：
viewController.m 中
#import "ViewController.h"
#import "blockTest.h"
@interfaceViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[superviewDidLoad];
blockTest *blockText = [[blockTestalloc]init];
[blockText startTimer];
blockText.showBlock = ^() {
UIAlertController *alert = [UIAlertControlleralertControllerWithTitle:@"alert"message:nilpreferredStyle:UIAlertControllerStyleAlert];
[alertaddAction:[UIAlertActionactionWithTitle:@"Cancel"style:UIAlertActionStyleDestructivehandler:nil]];
[selfpresentViewController:alertanimated:YEScompletion:nil];
};
}
@end
#import<Foundation/Foundation.h>
typedefvoid (^showAlertBlock)();
@interface blockTest :NSObject
@property (nonatomic,copy)showAlertBlock showBlock;
- (void)startTimer;
@end
blockTest.m中
#import "blockTest.h"
@implementation blockTest
- (void)startTimer {
[NSTimerscheduledTimerWithTimeInterval:5.0ftarget:selfselector:@selector(showAlert)userInfo:nilrepeats:YES];
}
- (void)showAlert {
if (self.showBlock) {
self.showBlock();
}
}
@end