Block详情

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //没有返回值
    //[self testNoReturnValue];
    //[self testIntReturnValue];
    //[self testNSStringReturnValue];
    [self test];
}
-(void)test
{
    //1.没有返回值,参数为对象类型
    void (^block1)(NSString *param) = ^(NSString *param){
        NSLog(@"%@",param);
    };
    block1(@"test");
    
    //2.返回值为对象类型,两个基本类型的参数
    NSString *(^block2)(int,int) = ^(int a,int b){
        return [NSString stringWithFormat:@"%d",a+b];
    };
    NSString *ret = block2(10,20);
    NSLog(@"%@",ret);
}

//有返回值,返回值为对象类型(NSString)
-(void)testNSStringReturnValue
{
    //1.没有参数
    NSString *(^block1)();
    block1 = ^{
      return @"你好";
    };
    NSString *ret1 = block1();
    NSLog(@"%@",ret1);
    
    //2.有一个参数,参数为基本类型
    NSString *(^block2)(int);
    block2 = ^(int age){
        return [NSString stringWithFormat:@"你今年%d岁",age];
    };
    NSString *ret2 = block2(10);
    NSLog(@"%@",ret2);
    
    //3.有一个参数,参数为对象类型
    NSString *(^block3)(NSString *);
    block3 = ^(NSString *name){
        return name;
    };
    NSString *ret3 = block3(@"小明");
    NSLog(@"%@",ret3);
    
    //4.有两个参数,参数都是对象类型
    NSString *(^block4)(NSString *,NSString *);
    block4 = ^(NSString *name1,NSString *name2){
        return [NSString stringWithFormat:@"%@,%@",name1,name2];
    };
    NSString *ret4 = block4(@"小明",@"小花");
    NSLog(@"%@",ret4);
}
//有返回值,返回值为基本类型
-(void)testIntReturnValue
{
    //1.没有参数
    int (^block1)(void);
    block1 = ^{
        return 200;
    };
    //使用
    int ret1 = block1();
    NSLog(@"%d",ret1);
    
    //2.有一个参数
    int (^block2)(int);
    block2 = ^(int age){
        return age;
    };
    //使用
    int ret2 = block2(50);
    NSLog(@"%i",ret2);
    
    //3.有一个参数,参数为对象类型
    int (^block3)(NSString *);
    block3 = ^(NSString *name){
        return (int)name.length;
    };
    int ret3 = block3(@"hello world");
    NSLog(@"%d",ret3);
    
    //4.有两个参数,两个对象类型
    int (^block4)(NSString *,NSString *);
    block4 = ^(NSString *name1,NSString *name2){
        return (int)(name1.length+name2.length);
    };
    int ret4 = block4(@"hello",@"world");
    NSLog(@"%i",ret4);
}

//没有返回值的
-(void)testNoReturnValue
{
    //1.没有参数
    //声明
    void (^block1)(void);
    //赋值
    block1 = ^{
        NSLog(@"void");
    };
    //使用
    block1();
    
    //2.没有返回值参数是基本类型
    //声明时的形参可以和赋值时不一样
    void (^block2)(int pa);
    //赋值
    block2 = ^(int param){
        NSLog(@"param = %d",param);
    };
    //使用
    block2(100);
    
    //3.有一个参数,参数是对象类型(NSString)
    //声明
    void (^block3)(NSString *);
    //赋值
    block3 = ^(NSString *name){
        NSLog(@"name = %@",name);
    };
    //使用
    block3(@"小明");
    
    //4.有两个参数,一个基本类型,一个对象类型
    void (^block4)(int,NSString *);
    block4 = ^(int age,NSString *name){
        NSLog(@"%@今年%d岁",name,age);
    };
    //使用
    block4(20,@"小明");
}

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

@end