代码块_iOS_2

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int multiplier = 7;

int/*myBlock是块对象，返回整型值。*/ (^myBlock)/*^符号将myBlock声明为一个块对象*/(int)/*它有一个参数，参数的类型也是整型值*/ =/*这是块对象的主体部分*/ ^(int num)/*参数名称是num*/{/*这是定义块对象的语法结构。这部分就是赋给myBlock变量的值。*/

return num * multiplier;

};

int result = myBlock(4);

DLog(@"result is %d",result);

// self.view.transform = CGAffineTransformMakeRotation(M_1_PI);

参数是NSString *的代码块

void (^printBlock)(NSString * x);

printBlock = ^(NSString * str)

{

NSLog(@"print:%@",str);

};

printBlock(@"hello world!");

代码用在字符串数组排序

NSArray * stringArray = [NSArrayarrayWithObjects:@"abc 1",@"abc 21",@"abc 12",@"abc 13",nil];

NSComparator sortBlock = ^(id string1,id string2){

return [string1 compare:string2];

};

NSArray * sortArray = [stringArray sortedArrayUsingComparator:sortBlock];

NSLog(@"sortArray:%@",sortArray);

代码块的递归调用

static void (^ const blocks)(int) = ^(int i){

if (i > 0) {

NSLog(@"num:%d",i);

blocks(i-1);

}

};

blocks(3);

在代码块中使用局部变量和全局变量

void(^block)(void) = ^(void)

{

global++;

NSLog(@"global %d",global);

};

block();

NSLog(@"global:%d",global);

__block int local =500;

void(^block1)(void) = ^(void)

{

local++;

NSLog(@"local:%d",local);

};

block1();

NSLog(@"local:%d",local);

NSArray * cards = [NSArrayarrayWithObjects:@"Jack",@"Queen",@"King",@"Ace",nil];

[cards enumerateObjectsUsingBlock:^(id obj,NSUInteger idx, BOOL *stop) {

NSLog(@"%@ card at index %d",obj,idx);

}];

void (^now)(void) = ^{

NSDate * date = [NSDatedate];

NSLog(@"The date and time is %@",date);

};

now();

int (^multiply)(int,int) = ^(int x,int y){

return x * y;

};

NSLog(@"multiply is %d",multiply(2,3));

int (^tripler)(int) = ^(int number) {

return number * 3;

};

typedef int (^ComputationBlock)(int);

[GigaHomeViewControlleriterateFromOneTo:5withBlock:tripler];

+ (void)iterateFromOneTo:(int)limit withBlock:(int (^)(int))block {

for (int i = 1; i <= limit; i++) {

int result = block(i);

NSLog(@"iteration %d => %d", i, result);

}

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