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ObjectC----Block用法以及用Block实现数组排序

2015-04-02 17:46 477 查看
// Created By 郭仔 2015年04月02日17:45:01

函数体外部分:
typedef int (^Block)(int ,int );//重命名
typedef void (^Block1)(int );
int n = 0;
=================================================================================================================

// 定义函数指针
int (*p)(int ,int) = sum;

//通过函数指针调用函数
int re = p(10,3);
printf("%d\n",re);
// int n = 4;


Block block = ^(int x,int y){
// NSLog(@"%d",n);
return x+y;
};
NSLog(@"%d",block(1,1));


//定义block
int (^block1)(int,int) = ^(int x,int y){
return x+y;
}; //最后分号别忘了


//调用block
int result = block1(10,34);
printf("%d\n",result);


//两个练手例子
void (^block2)(int) = ^(int num){
printf("%d\n",num);
};
int (^block3)(int) = ^(int year){
return year;
};
block2(4);
printf("%d\n",block3(5));


int (^block4)(NSString *) = ^(NSString * str){
return [str intValue]; //对象方法intValue实现字符串转化为数值
};
NSLog(@"%d",block4(@"333"));
//printf("%d\n",block4(@"333"));

/*

block是匿名函数:因为调用函数有两种方式,一种是通过函数名调用,另一种是通过函数指针调用;

通过函数指针调用函数之前,需要给函数指针赋值,也需要用到函数名,所以对于匿名函数来说,这两种方式都不能实现函数的调用,因此使用block;

block和函数指针非常相似,但是有本质上的区别,但在使用方面,区别不大,我们可以将block当成函数指针,这样简化blcok的使用;
*/
__block int x = 10;
// int y;
Block1 block5 = ^(int num){


x++;
// y++;//局部变量
n ++; //全局变量
NSLog(@"%d",x);
NSLog(@"%d",num);
};


block5(5);




/*

1.在block里面能访问block之外的局部变量,不能修改block之外的局部变量,如果需要修改,该局部变量前面加__block;

2.在block中可以修改全局变量的值;

3.__block声明的变量会存储在内存的全局区(静态区)
*/




// =================================================================


Car * car1 = [Car carWithType:@"aa" andColor:@"bb" andPrice:134 andMaxSpeed:133 andCostOil:17];


Car * car2 = [Car carWithType:@"cc" andColor:@"dd" andPrice:234 andMaxSpeed:233 andCostOil:27];


Car * car3 = [Car carWithType:@"ee" andColor:@"ff" andPrice:334 andMaxSpeed:333 andCostOil:37];


Car * car4 = [Car carWithType:@"gg" andColor:@"hh" andPrice:434 andMaxSpeed:433 andCostOil:47];


NSMutableArray * cars = [NSMutableArray arrayWithObjects:car1,car2,car3,car4, nil];


//价格从高到低排序 block排序
//若用sortedArrayUsingComparator则需要重新定义一个数组保存(因为有返回值)
[cars sortUsingComparator:^NSComparisonResult(Car *obj1, Car *obj2) {
if ([obj1 price]<[obj2 price]) {
return NSOrderedDescending;
}
else if ([obj1 price] == [obj2 price])
return NSOrderedSame;
else
return NSOrderedAscending;
}];


for (Car *car in cars) {
NSLog(@"%@",car);
}


// maxSpeed从大到小排序,使用sortedUsingComparator
NSArray * arr = [cars sortedArrayUsingComparator:^NSComparisonResult(Car *obj1, Car *obj2) {
if ([obj1 maxSpeed]<[obj2 maxSpeed]) {
return NSOrderedDescending;
}
else if ([obj1 maxSpeed]==[obj2 maxSpeed])
return NSOrderedSame;
else
return NSOrderedAscending;
}];


for (Car * car in arr) {
NSLog(@"%@",car);
}




//自己定义block
NSComparisonResult (^block6)(Car *,Car*) = ^(Car *obj1,Car *obj2){
if ([obj1 maxSpeed]<[obj2 maxSpeed]) {
return NSOrderedDescending;
}
else if ([obj1 maxSpeed]==[obj2 maxSpeed])
return NSOrderedSame;
else
return NSOrderedAscending;


};
//然后调用sort方法,block6传参过去
[cars sortUsingComparator:block6];


for (Car * car in cars) {
NSLog(@"%@",car);
}


// ==============================================================
//字面量
//数组字面量
NSString * str = @"Literals";
//数组字面量
NSArray * arr1 = @[@"1",@"2",@"3"];
for (NSString * s in arr1) {
NSLog(@"%@",s);
}
//字典字面量
NSDictionary * dic = @{@"name":@"zhangsan",@"age":@"6"};
NSLog(@"%@,%@",dic[@"name"],dic[@"age"]);




NSNumber * num = @123;//把数字123转化成NSNumber对象
NSLog(@"%@",num);
// ===============================================================
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