Objective-C学习笔记之for( int )机制

NSArray *myArray = [NSArray arrayWithObjects:@"1",@"2",@"3",@"4",nil];//初始多个元素的数组

//或者NSArray *myArray = @[@"1",@"2",@"3",@"4"];

//快速枚举

for(id/*NSString*/ obj in myArray)

{

NSLog(@"%@",obj);

}

它跟平时我们用的效果是一样的

for(NSUInteger number = 0 ; number<myArray.count/*数组长度*/ ; number++)

{

NSString* str = [myArray objectAtIndex:number];

NSLog(@"%@", str);

//或者NSLog(@"%@",myArray[number]);

}

//通过实验得出结论:枚举过程中数组不能改变,否则会抛出异常,下面提供了一个遍历时想要改变数组的办法

         NSMutableArray *arr1 = [NSMutableArray arrayWithObjects:@"",@"",@"",nil];
         NSMutableArray *arr2 = [NSMutableArray arrayWithArray:arr1];//将arr1复制给arr2
         //遍历arr2，处理arr1
         int i=;
         for( id num in arr2)
         {
             if([num isEqualToString:@""])
                 arr1[i] = @"";
             i++;
         }
         NSLog(@"%@",arr1);

结果将@“456”替换为@“555”；