#import 
     
      int main(int argc, const char * argv[]){    //数组中建议存储同类型的数据元素        NSArray * array = @[@"one",@"two",@"three"];    for (int i = 0; i < array.count; i++) {        NSString * str = array[i];        NSLog(@"array[%d] = %@",i,str);    }    //使用增强for循环遍历数组    for (NSString * str in array) {        NSLog(@"%@",str);    }        return 0;}
     

#import 
     
      int main(int argc, const char * argv[]){            NSArray * array = @[@"1",@"2",@"3",@"4"];        NSLog(@"before sort%@",array);                //排序        NSComparisonResult  cmp = [@"a" compare:@"b"];        //        NSLog(@"%d",cmp);        array = [array sortedArrayUsingSelector:@selector(compare:)];        //正序 左边小于右边                NSLog(@"after sort %@",array);                //(void)(^block)(int a ,int b);        NSArray * arry1 = [array sortedArrayUsingComparator:^NSComparisonResult(id obj1,id obj2)        {            return [obj1 compare:obj2];        }];}