数组中元素按照一定规则排序
主要是NSSortDescriptor这个类 代码
NSArray *array = @[@"one", @"two", @"three", @"four", @"six"];
//创建一个排序条件，也就是一个NSSortDescriptor对象
//其中第一个参数为数组中对象要按照什么属性来排序(比如自身、姓名，年龄等)
//第二个参数为指定排序方式是升序还是降序
//ascending 排序的意思，默认为YES 升序
NSSortDescriptor *des = [[NSSortDescriptor alloc] initWithKey:@"self" ascending:YES];
NSArray *newArray = [array sortedArrayUsingDescriptors:@[des]];
NSLog(@"%@",newArray);
多条件排序
Person *p1 = [[Person alloc] initWithName:@"zhonger" age:@"19"];
Person *p2 = [[Person alloc] initWithName:@"zhubada" age:@"11"];
Person *p3 = [[Person alloc] initWithName:@"zhubada" age:@"1"];
Person *p4 = [[Person alloc] initWithName:@"zhubada" age:@"33"];
Person *p5 = [[Person alloc] initWithName:@"hehehe" age:@"38"];
NSArray *person = @[p1, p2, p3, p4, p5];
NSSortDescriptor *des1 = [[NSSortDescriptor alloc]initWithKey:@"name" ascending:NO];
NSSortDescriptor *des2 = [[NSSortDescriptor alloc] initWithKey:@"age" ascending:NO];
// 可以用sortedArrayUsingDescriptors:方法实现把多个排序条件放到数组中，实现多条件排序，按数组先后顺序，先加入的优先级高
NSArray *newArray1 = [person sortedArrayUsingDescriptors:@[des1,des2]];
for (Person *p in newArray1) {
NSLog(@"姓名：%@ , 年龄：%@",p.name,p.age);
}
注意这两个方法 可变数组和不可变数组
Snip20170321_3.png
