函数式编程思想-计算器-Calculate

1.一般编程

Calculate.h

#import 

@interface Calculate : NSObject
@property (nonatomic,assign) int result;
- (instancetype)add:(int)num;
@end

Calculate.m

#import "Calculate.h"

@implementation Calculate
- (instancetype)add:(int)num{
    _result += num;
    return self;
}
@end

ViewController.m

#import "ViewController.h"
#import "Calculate.h"

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    Calculate *calculate = [Calculate new];
    int result = [[[[[[[calculate add:1] add:2] add:3] add:4] add:5] add:6] result];
    NSLog(@"result = %d",result);
    // 2016-08-14 17:15:13.444 Calculate[19636:1580250] result = 21
}
@end

2.函数式编程思想

函数式编程思想:把操作尽量写成一系列嵌套的函数或方法调用
函数式编程特点:方法必须返回本身对象，参数是block，该block的参数是需要操作的值，该block的返回值是操作的结果

Calculate.h

#import 
@interface Calculate : NSObject
@property (nonatomic,assign) int result;
- (instancetype)add:(int (^) (int result))block;
@end

Calculate.m

#import "Calculate.h"

@implementation Calculate
- (instancetype)add:(int (^) (int result))block{
    _result = block(_result);
    return self;
}
@end

ViewController.m

- (void)viewDidLoad{
    [super viewDidLoad];
    
    Calculate *calculate = [Calculate new];
    int result = [[calculate add:^int(int result) {
        result += 1;
        result += 2;
        result += 3;
        result += 4;
        result += 5;
        
        return result;
    }] result];
    NSLog(@"result = %d",result);
    // 2016-08-14 17:32:15.356 Calculate[21322:1595078] result = 15
}

3.函数化更进一层

Calculate.h

#import 

@interface Calculate : NSObject
@property (nonatomic,assign) int result;
@property (nonatomic,assign) BOOL isEqual;
- (instancetype)add:(int (^) (int result))block;
- (instancetype)equal:(BOOL (^) (int result))block;
@end

Calculate.m

#import "Calculate.h"

@implementation Calculate
- (instancetype)add:(int (^) (int result))block{
    _result = block(_result);
    return self;
}

-(instancetype)equal:(BOOL (^)(int))block{
    _isEqual = block(_result);
    return self;
}
@end

ViewController.m

#import "ViewController.h"
#import "Calculate.h"

@implementation ViewController

- (void)viewDidLoad{
    [super viewDidLoad];
    
    Calculate *calculate = [Calculate new];
    BOOL isEqual = [[[calculate add:^int(int result) {
        result += 1;
        result += 2;
        result += 3;
        result += 4;
        result += 5;
        
        return result;
    }] equal:^BOOL(int result) {
        return (result == 15);
    }] isEqual];
    NSLog(@"isEqual = %d",isEqual);
    // 2016-08-14 17:47:29.657 Calculate[22823:1608283] isEqual = 1
}
@end