101. NSSortDescriptor排序

简介

NSSortDescriptor 可以用于对数组的排序, 可对普通数组进行简单排序, 也可以按照指定的对象的属性(或者字典的 key 值)对对象数组(或字典数组)进行排序。排序的方法分为正序和倒序两种.

方法

排列数组分为对 NSSet, NSArray, NSMutableArray,NSOrderedSet,NSMutableOrderedSet的排序, 这里只讲对数组的排序:
不可变数组方法:
-(NSArray )sortedArrayUsingDescriptors:(NSArray

简单数组排序

这里的简单数组是指数组元素为简单对象的数组, 如下面的存储着字符串对象, 或者NSNumber 等的数组.
简单数组排序 descriptionKey 可以为 nil 就能够将顺序排列好.

    NSMutableArray *numArr = [[NSMutableArray alloc] init];    [numArr addObject:@"2"];    [numArr addObject:@"1"];    [numArr addObject:@"3"];    NSSortDescriptor *sd_num = [NSSortDescriptor sortDescriptorWithKey:nil ascending:NO];    NSArray *arr1 = [numArr sortedArrayUsingDescriptors:[NSArray arrayWithObjects:sd_num, nil]];    for (NSString *str in arr1) {        NSLog(@"%@", str);    }    NSMutableArray *letterArr = [[NSMutableArray alloc] init];    [letterArr addObject:@"b"];    [letterArr addObject:@"c"];    [letterArr addObject:@"a"];    NSSortDescriptor *sd_letter = [NSSortDescriptor sortDescriptorWithKey:nil ascending:YES];    NSArray *arr2 = [letterArr sortedArrayUsingDescriptors:[NSArray arrayWithObjects:sd_letter, nil]];    for (NSString *str in arr2) {        NSLog(@"%@", str);    }

打印结果:

字典数组排序

如果是Employee对象或者字典数组, 就需要按照key 值来排序.

 NSMutableArray *nameArr = [[NSMutableArray alloc] init];    NSMutableDictionary *person1 = [[NSMutableDictionary alloc] init];    [person1 setObject:@"zhangsan" forKey:@"name"];    NSMutableDictionary *person2 = [[NSMutableDictionary alloc] init];    [person2 setObject:@"lisi" forKey:@"name"];    NSMutableDictionary *person3 = [[NSMutableDictionary alloc] init];    [person3 setObject:@"wangwu" forKey:@"name"];    [nameArr addObject:person1];    [nameArr addObject:person2];    [nameArr addObject:person3];    NSSortDescriptor *sd_name = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];    NSArray *arr3 = [nameArr sortedArrayUsingDescriptors:[NSArray arrayWithObjects:sd_name, nil]];    for (NSMutableDictionary *md in arr3) {        NSLog(@"%@", [md objectForKey:@"name"]);    }

打印结果: