关于Block初识与自己的认识

前些天学到了Block，对于Block有了一些大致的认识

Block是什么？

我认为是一些行为的封装 

举个例子  要将两个参数进行加减乘除   

创建4个Block实现价钱乘除四个操作即可  

用一个方法  传两个参数和一个block  返回就是block对这两个参数的操作

代码演示

#import <Foundation/Foundation.h>
#import "Calc.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // typedef
        Calc * calc = [[Calc alloc] init];
//        NSLog(@"%d",[calc calculateWithNumber1:3 andNumber2:5 withCalBlock:^int(int a, int b) {
//            return a-b;
//        }]);
        
        NSLog(@"%d",[calc calculateWithNumber1:2 andNumber2:5 withCalBlock:^int(int q, int w) {
            return q*w;
        }]);
//        NSLog(@"%d",[calc calculateWithNumber1:3 andNumber2:6 withCalcBlock:^int(int a, int b) {
//            return a*b;
//        }]);
    }
    return 0;
}

#import <Foundation/Foundation.h>

typedef int (^CalcBlock) (int,int); // 定义一个block类型,类型的名称为CalcBlock
@interface Calc : NSObject
- (int)calculateWithNumber1:(int)num1 andNumber2:(int)num2 withCalBlock:(int (^)(int,int))calBlock;
- (int)calculateWithNumber1:(int)num1 andNumber2:(int)num2 withCalcBlock:(CalcBlock)calcBlock;
- (int)calculateWithNumber1:(int)num1 andNumber2:(int)num2 withSel:(SEL)sel;

@end

#import "Calc.h"

@implementation Calc
- (int)calculateWithNumber1:(int)num1 andNumber2:(int)num2 withCalBlock:(int (^)(int,int))calBlock {
    return calBlock(num1,num2);
}

- (int)calculateWithNumber1:(int)num1 andNumber2:(int)num2 withCalcBlock:(CalcBlock)calcBlock {
    return calcBlock(num1,num2);
}

@end

Block语法

 返回值(^Block名称)(参数列表) = ^返回值(参数列表){};

使用Blcok实现数组排序   根据Block返回值的不同来实现从大到小或从小到大的排序

以下代码   在循环遍历事 可以用Block来控制数组元素交换的条件 从而达到排序效果

 

#import <Foundation/Foundation.h>
#import "NSArray+Extention.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSArray * array = @[@"b",@"f",@"d",@"a",@"c"];
        NSArray * array2 = [array sortedArrayByBlock:^BOOL(id obj1, id obj2) {
            return [obj1 isGreaterThan:obj2];
        }];
        [array2 show];
        
        
    }
    return 0;
}

#import <Foundation/Foundation.h>

//扩展？
@interface NSArray (Extention)
- (void)show;
- (NSArray *)sortedArrayByBlock:(BOOL(^)(id,id))cmp;
@end

#import "NSArray+Extention.h"

@implementation NSArray (Extention)
- (void)show {
    for (id obj in self) {
        NSLog(@"%@",obj);
    }
}

- (NSArray *)sortedArrayByBlock:(BOOL (^)(id, id))cmp {
    NSMutableArray * muarray = [NSMutableArray arrayWithArray:self];
    for (int i = 0; i<self.count - 1; i++) {
        for (int j = 0; j< self.count-1-i; j++) {
            //引入Block方法
            if (cmp(muarray[j],muarray[j+1])) {
                [muarray exchangeObjectAtIndex:j withObjectAtIndex:j+1];
            }
        }
    }
    return [muarray copy];
}


@end

然后是老师的一个例子  用Block实现Boss让Worker买电脑

虽然我能看懂代码  但实在不理解 这样做的意义。。  Block的意义在于把Boss的电脑个数增加 

附上代码 

#import <Foundation/Foundation.h>
#import "Boss.h"
#import "Worker.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Worker * worker = [[Worker alloc] init];
        Boss * boss = [[Boss alloc] init];
        [boss showMacbooks];
        [worker buyMacbookWithNum:12 withSendFinishedBlock:^(int num) {
            boss.numOfMacbooks += num;
        }];
        [boss showMacbooks];
    }
    return 0;
}

#import <Foundation/Foundation.h>
#import "Worker.h"
@interface Boss : NSObject
@property (nonatomic,assign) int numOfMacbooks;
- (void)showMacbooks;
@end

#import "Boss.h"

@implementation Boss
- (void)showMacbooks {
    NSLog(@"老板现在有Macbook%d台",_numOfMacbooks);
}

@end

#import <Foundation/Foundation.h>

@interface Worker : NSObject
- (void)buyMacbookWithNum:(int)num withSendFinishedBlock:(void(^)(int))sentBlock;
@end

#import "Worker.h"

@implementation Worker
- (void)buyMacbookWithNum:(int)num withSendFinishedBlock:(void(^)(int))sentBlock{
    NSLog(@"买了%d台Macbook",num);
    NSLog(@"给老板%d台",num);
    sentBlock(num);
}
@end