ios数组排序

- (void) sortMethod {
    NSComparator cmptr = ^(id obj1, id obj2) {
        if ([obj1 integerValue] > [obj2 integerValue]) {
            return (NSComparisonResult)NSOrderedDescending;
        }
        
        if ([obj1 integerValue] < [obj2 integerValue]) {
            return (NSComparisonResult)NSOrderedAscending;
        }
        
        return (NSComparisonResult) NSOrderedSame;
    };
    
    NSArray *sortArray = [[NSArray alloc] initWithObjects:@"1",@"3",@"4",@"7",@"8",@"2",@"6",@"5",@"13",@"15",@"12",@"20",@"28",@"",nil];

    //排序前
    NSLog(@"排序前:%@",[self formatOutPut:sortArray]);
    
    //第一种排序
    NSArray * array = [sortArray sortedArrayUsingComparator:cmptr];
    
    NSLog(@"排序后:%@",[self formatOutPut:array]);
    
    //第二种排序：利用sortedArrayUsingFunction 调用 对应方法customSort，这个方法中的obj1和obj2分别是指数组中的对象。

    array = [sortArray sortedArrayUsingFunction:customSort context:nil];
    NSLog(@"排序后:%@",[self formatOutPut:array]);

    
}

- (NSString *) formatOutPut:(NSArray *) array {
    NSMutableString * output = [[NSMutableString alloc] init];
    for (NSString * str in array) {
        [output appendFormat:@"%@ ",str];
    }

    return [output autorelease];
}
              

NSInteger customSort(id obj1, id obj2,void* context){
    if ([obj1 integerValue] > [obj2 integerValue]) {
        return (NSComparisonResult)NSOrderedDescending;
    }
    
    if ([obj1 integerValue] < [obj2 integerValue]) {
        return (NSComparisonResult)NSOrderedAscending;
    }
    
    return (NSComparisonResult)NSOrderedSame;
};