链式编程

• 链式编程思想:下一级的block给上一级使用

• 思想:把需要做的事情封装到block，给外接提供一个block方法

• 特点：方法返回值需要是block。block参数:放需要操作的内容，block返回值：方法调用者。都是点语法。

• 代表：masonry框架

massory：
[view mas_makeConstraints:^(MASConstraintMaker *make){
    make.left.top.equalTo(@10);
    make.right.bottom.equalTo(@(-10));
}


void(^block)(MASConstraintMaker *make) = ^(MASConstraintMaker *make){
    make.left.top.equalTo(@10);
    make.right.bottom.equalTo(@(-10));
};
[view mas_makeConstraints:block];

====================

计算器Demo:
#import 
@interface CaculatorMaker : NSObject
@property (assign, nonatomic) int reslut;

- (CaculatorMaker *(^)(int num))add;
- (CaculatorMaker *(^)(int num))multy;
@end

#import "CaculatorMaker.h"
@implementation CaculatorMaker

- (CaculatorMaker *(^)(int num))add
{
    return ^(int num){

        _reslut += num;

        return  self;
    };
}
- (CaculatorMaker *(^)(int num))multy
{
    return ^(int num){

        _reslut *= num;

        return self;
    };
}
@end

#import 
#import "CaculatorMaker.h"
@interface NSObject (Caculator)

//计算机都使用这个方法，一调用这个方法就返回结果
+ (int)makeCaculator:(void(^)(CaculatorMaker *))block;
@end

#import "NSObject+Caculator.h"
@implementation NSObject (Caculator)

+ (int)makeCaculator:(void(^)(CaculatorMaker *))block
{
    //创建计算对象
    CaculatorMaker *maker = [[CaculatorMaker alloc] init];

    //计算
    block(maker);
    return maker.reslut;
}
@end


- (void)viewDidLoad {
    [super viewDidLoad];

    int result = [NSObject makeCaculator:^(CaculatorMaker *maker) {

        //把所有的计算代码封装到这里
        maker.add(10).add(20).multy(3);
    }];

    NSLog(@"%d",result);
}