链式编程

链式编程的特点

链式编程通过点语法连续调用函数，将一系列代码执行动作串联起来，让代码更加简洁, 可读性更强，不用单独一个一个的执行。

Objective-C和Swift代码写法上有些差别

Objective-C
对象方法的返回值是一个Block,在返回Block函数中做相应的逻辑处理并返回当前对象

Swift
对象方法的返回值是当前对象，需要操作的值以形参传入

OC版

CaculateMake 具体方法类

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

@interface CaculateMake : NSObject

/** 结果 */
@property (nonatomic, assign) CGFloat result;

- (CaculateMake *(^)(CGFloat))add;

- (CaculateMake *(^)(CGFloat))sub;

@end


####CaculateMake.m
#import "CaculateMake.h"

@implementation CaculateMake

- (CaculateMake *(^)(CGFloat))add {
    return ^CaculateMake *(CGFloat value) {
        self.result += value;
        return self;
    };
}

- (CaculateMake *(^)(CGFloat))sub {
    return ^CaculateMake *(CGFloat value) {
        self.result -= value;
        return self;
    };
}

@end

点语法调用类

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

@interface Caculate : NSObject

+ (CGFloat)caculate:(void(^)(CaculateMake *make))caculateBlock;

@end

#import "Caculate.h"

@implementation Caculate

+ (CGFloat)caculate:(void (^)(CaculateMake *))caculateBlock {
    
    CaculateMake *make = [[CaculateMake alloc] init];
    caculateBlock(make);
    return make.result;
}

@end

Swift版

class CaculateMake {
    
    var result: Int = 0
    
    func add(num: Int) -> CaculateMake {
        result += num
        return self
    }
    
    
    func sub(num: Int) -> CaculateMake {
        result -= num
        return self
    }
    
}

class Caculate {
    
    static func beginCaculate(caculateBlock: (CaculateMake) -> ()) -> Int {
        let caculateMake = CaculateMake()
        caculateBlock(caculateMake)
        return caculateMake.result
    }
    
}

#### 使用
let n = Caculate.beginCaculate { (make) in
    make.add(num: 10).add(num: 20)
}