对数组进行排序

对于简单对象,及系统自带的,例如:NSString,NSNumber,NSMutableArray等可用sortedArrayUsingSelector或sortUsingSelector
1.不可变数组

NSArray *array1 = @[@"11",@"a",@"mm",@"ii",@"tr",@"oo",@"rt"];

NSArray *sortArray = [array1 sortedArrayUsingSelector:@selector(compare:)];
        NSLog(@"sortArray = %@",sortArray);

2.把数组一的值拷贝给给变数值二,可变数组

NSMutableArray *array2 = [NSMutableArray arrayWithArray:array1];

//可变数组排序,没有返回值.参数类型是SEL那么代表此参数是个方法

  [array2 sortUsingSelector:@selector(compare:)];
NSLog(@"array2 = %@",array2);

3.不可变 数组中存储复杂对象时

   Person *per1 = [Person personName:@"m淼淼" sex:@"女" age:18];
        Person *per2 = [Person personName:@"x香香" sex:@"女" age:22];
        Person *per3 = [Person personName:@"w王发" sex:@"男" age:32];
        Person *per4 = [Person personName:@"z张静" sex:@"女" age:20]; 
NSArray *arr1 = @[per1,per2,per3,per4];    
```c
//NSSortDescriptor *description1 = [NSSortDescriptor sortDescriptorWithKey:arr1 ascending:YES];数组arr1中存储的是复杂对象,是不可以使用sort方法进行排序的.因为compare只适用于系统的简单对象进行排序
```c
NSSortDescriptor *description1 = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:NO];
        NSArray *newArray1 = [arr1 sortedArrayUsingDescriptors:@[description1]];
        //遍历数组输出结果
        for (Person *p in newArray1) {
            NSLog(@"des1=%@", p);
        }

4.定义可变数组,进行排序,按名字降序排序

NSMutableArray *mArray = [NSMutableArray arrayWithArray:arr1];
        NSSortDescriptor *des2 = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:NO];
        [mArray sortedArrayUsingDescriptors:@[des2]];
        for (Person *p in mArray) {
            NSLog(@"%@des2", p);