字符串、集合补充

1.数组与字符间转换

componentsSeparatedByString：将字符串以x分割成数组

componentsJoinedByString：将数组以x拼接为字符串

2.排序

Description：按描述条件(“一般字符对象”或对象的属性)排序.

注意可变排序方法和不可排序方法的是否有返还值.

    NSString *str = @"123-456-789-000";
    NSArray *arr = [str componentsSeparatedByString:@"-"];
    NSLog(@"%@",arr);
    NSString *str2 = [arr componentsJoinedByString:@""];//数组转为字符串
    NSLog(@"%@",str2);
    
    NSMutableArray *arr2 = [[NSMutableArray alloc]init];
    [arr2 addObject:@"1"];
    [arr2 insertObject:@"3" atIndex:0];
    [arr2 addObject:@"2"];
    NSLog(@"%@",arr2);
    //系统的compara：适合字符串，不适合对象排序
    //2
    NSSortDescriptor *sort1 = [NSSortDescriptor sortDescriptorWithKey:nil ascending:YES];//nil或self
    [arr2 sortUsingDescriptors:[NSArray arrayWithObject:sort1]];//注意可变排序方法和不可排序方法的区别
    
    NSLog(@"%@",arr2);
    //3复杂对象的排序
    Student *s1 = [[Student alloc]init];
    s1.name = @"obanma";
    
    Student *s2 = [[Student alloc]init];
    s2.name = @"jobs";
    
    Student *s3 = [[Student alloc]init];
    s3.name = @"bill";
    
    NSMutableArray *arr3 = [NSMutableArray arrayWithObjects:s1,s2,s3,nil];
    
    NSSortDescriptor *sort2 = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];//kvc
    
    [arr3 sortUsingDescriptors:[NSArray arrayWithObject:sort2]];
    
    for (Student *stu in arr3)
    {
        NSLog(@"stu.name = %@",stu.name);
    }

Comparator：通过代码块对”对象或对象属性“排序

Student *s1 = [[Student alloc]init];
    s1.name = @"obanma";
    s1.age = 38;
    Student *s2 = [[Student alloc]init];
    s2.name = @"jobs";
    s2.age = 17;
    Student *s3 = [[Student alloc]init];
    s3.name = @"bill";
    s3.age = 25;
    NSArray *array = [[NSArray alloc]initWithObjects:s1,s2,s3,nil];
    // 升序排列name和age。降序的话，调换ascend和descaend位置。
    
    NSArray *sortAge = [array sortedArrayUsingComparator:^(id obj1,id obj2)
                        {
                            if([obj1 age] < [obj2 age])
                            {
                                return (NSComparisonResult)NSOrderedAscending;//-1
                            }
                            else if ([obj1 age] > [obj2 age])
                            {
                                return (NSComparisonResult)NSOrderedDescending;
                            }
                            
                            return (NSComparisonResult)NSOrderedSame;
                        }];

    for (Student *stu in sortAge)
    {
        NSLog(@"stu.age = %d",stu.age);//38,17,25
    }
    
    NSArray *sortArr = [array sortedArrayUsingComparator:^(id obj1,id obj2)
                        {
                            NSLog(@"%d",[[obj1 name] compare: [obj2 name]]);
                            
                            if ([[obj1 name] compare: [obj2 name]] == NSOrderedDescending)//1
                            {
                                return (NSComparisonResult)NSOrderedDescending;//1
                            }
                            else if([[obj1 name] compare: [obj2 name]] == NSOrderedAscending)
                            {
                                return (NSComparisonResult)NSOrderedAscending;//-1
                            }
                            return (NSComparisonResult)NSOrderedSame;
                        }];
    
    for (Student *stu in sortArr)
    {
        NSLog(@"stu.name = %@",stu.name);
    }

http://blog.csdn.net/xiaoxuan415315/article/details/9198729

http://blog.csdn.net/shx_yi/article/details/8687368