一、什么是链式编程？

链式编程，是指将多个方法用点语法链接起来。
1）让代码更加简洁；
2）可读性更强；
3）编程性强；
4）对程序员的业务能力要求高；
5）不太利于代码调试。 

二、调用代码，如下：

//
//  ViewController.m
//  链式编程Demo
//
//  Created by ghk on 2018/11/4.
//  Copyright © 2018年 ghk. All rights reserved.
//

#import "ViewController.h"
#import "Tool.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    float result = [Tool make:^(Tool *tool) {

        tool.add(1).add(2).add(3).subtract(1).ride(5).divide(4);
    }];

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


@end

三、Tool实现代码，如下：

//
//  Tool.h
//  链式编程Demo
//
//  Created by ghk on 2018/11/4.
//  Copyright © 2018年 ghk. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Tool : NSObject

typedef Tool * (^Block)(NSInteger number);

/** 加法 */
@property (nonatomic, copy, readonly) Block add;
/** 减法 */
@property (nonatomic, copy, readonly) Block subtract;
/** 乘法 */
@property (nonatomic, copy, readonly) Block ride;
/** 除法 */
@property (nonatomic, copy, readonly) Block divide;

+ (float)make:(void (^)(Tool *tool))block;

@end

//
//  Tool.m
//  链式编程Demo
//
//  Created by ghk on 2018/11/4.
//  Copyright © 2018年 ghk. All rights reserved.
//

#import "Tool.h"

@interface Tool ()

@property (nonatomic, assign) float result;

@end

@implementation Tool

- (void)dealloc
{
    NSLog(@"%s",__func__);
}

+ (float )make:(void (^)(Tool *tool))block {

    if (block) {

        Tool *tool = [[Tool alloc] init];
        block(tool);
        return tool.result;
    }
    return 0;
}

- (Block)add {

    return ^(NSInteger number) {

        float newResult = self.result;
        newResult += number;
        NSLog(@" %f ＋ %zi = %f",self.result,number,newResult);
        self.result = newResult;

        return self;
    };
}

- (Block)subtract {

    return ^(NSInteger number) {

        float newResult = self.result;
        newResult -= number;
        NSLog(@" %f － %zi = %f",self.result,number,newResult);
        self.result = newResult;

        return self;
    };
}

- (Block)ride {

    return ^(NSInteger number) {
        float newResult = self.result;
        newResult *= number;
        NSLog(@" %f × %zi = %f",self.result,number,newResult);
        self.result = newResult;
        return self;
    };
}

- (Block)divide {

    return ^(NSInteger number) {
        float newResult = self.result;
        newResult /= number;
        NSLog(@" %f ÷ %zi = %f",self.result,number,newResult);
        self.result = newResult;
        return self;
    };
}

@end

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