OC数组排序的基本方法

OC中数组排序的三中方法：

sortedArrayUsingSelector:
sortedArrayUsingComparator:
sortedArrayUsingDescriptors:

一，简单排序（sortedArrayUsingSelector:）

如果只是对字符串的排序，可以利用sortedArrayUsingSelector:方法就可以，代码如下

void sortArray(){
NSArray *array = [NSArray arrayWithObjects:@"abc",@"456",@"123",@"789",@"ef",nil];
NSArray *sortedArray = [array sortedArrayUsingSelector:@selector(compare:)];
NSLog(@"%@",sortedArray);
}

除了利用字符串自带的compare：方法，也可以自己写compare：方法，进行对象的比较。

先建立Person类

#import "Person.h"
@implementation Person
//直接实现静态方法，获取带有name和age的Person对象
+(Person *)personWithAge:(int) age withName:(NSString *)name
{
Person *person = [[Person alloc]init];
Person.age = age;
Person.name = name;
return person;
}

自定义排序方法：

- (NSComparisonResult)comparePerson:(Person *)
{
//默认按年龄排序
NSComparisonResult result = [NSNumber numberWithInt:person.age] compare:[NSNumber numberWithInt:self.age];
//如果年龄一样，就按照名字排序
if (result == NSOrderedSame)
{
result = [self.name compare:person.name];
}
return result;
}
@end

主函数代码：

void sortArray()
{
Person *p1 = [Person personWithAge:23 withName:@"zhangsan"];
Person *p2 = [Person personWithAge:21 withName:@"lisi"];
Person *p3 = [Person personWithAge:24 withName:@"wangwu"];
Person *p4 = [Person personWithAge:24 withName:@"liwu"];
Person *p5 = [Person personWithAge:20 withName:@"liwu"]';
NSArray *array = [NSArray arrayWithObjects:p1,p2,p3,p4,p5,nil];
}

二，利用block语法（sortedArrayUsingComparator:）

苹果官方提供了block语法，其中数组排序可以用sortedArrayUsingComparator:方法

void sortArray()
{
NSArray *array = [NSArray arrayWithObjects:@"1bc",@"4bc",@"4b6",@"123",@"3ef",nil];
NSArray *sortedArray = [array sortedArrayUsingComparator:^NSComparisonResult(id obj1,id obj2){
//这里的代码可以参照上面compare：默认的排序方法，也可以把自定义的方法写这里，给对象排序
NSComparisonResult result = [obj1 compare:obj2];
return result;
}];
NSLog(@"排序后：%@",sortedArray);
}

三，高级排序（sortedArrayUsingDescriptors:）

如果是这样一种情况呢？Person类里有另外一个类的变量，比如说Person类除了name，age变量，还有一辆车Car类型，

Car类里有个name属性。对Person对象进行排序，有这样的要求：按照Car的name排序，如果是同一辆车，也就是Car

的name相同，那么再按照年龄进行排序，如果年龄也相同，最后按照Person的name进行排序。

Car.m实现

#import "Car.h"
@implementation Car

+(Car *)initWithName:(NSString *)name{
Car *car = [Car alloc] init];
car.name = name;
return car;
}@end

Person.m

#import "Person.h"
#import "Car.h"
@implementation Person

+(Person *)personWithAge:(int)age withName:(NSString *)name withCar:(Car *)car{
Person *person = [[Person alloc] init];
person.age = age;
person.name = name;
person.car = car;
return person;
}

//这里重写description方法，用于最后测试排序结果显示
-(NSString *)description{
return [NSString stringWithFormat:@"age is %zi , name is %@, car is %@",_age,_name,_car.name];
}

@end

主函数

void sortArray4(){
//首先来3辆车，分别是奥迪、劳斯莱斯、宝马
Car *car1 = [Car initWithName:@"Audio"];
Car *car2 = [Car initWithName:@"Rolls-Royce"];
Car *car3 = [Car initWithName:@"BMW"];

//再来5个Person，每人送辆车，分别为car2、car1、car1、car3、car2
Person *p1 = [Person personWithAge:23 withName:@"zhangsan" withCar:car2];
Person *p2 = [Person personWithAge:21 withName:@"zhangsan" withCar:car1];
Person *p3 = [Person personWithAge:24 withName:@"lisi" withCar:car1];
Person *p4 = [Person personWithAge:23 withName:@"wangwu" withCar:car3];
Person *p5 = [Person personWithAge:23 withName:@"wangwu" withCar:car2];

//加入数组
NSArray *array = [NSArray arrayWithObjects:p1,p2,p3,p4,p5, nil];

//构建排序描述器
NSSortDescriptor *carNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"car.name" ascending:YES];
NSSortDescriptor *personNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];
NSSortDescriptor *personAgeDesc = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:YES];

//把排序描述器放进数组里，放入的顺序就是你想要排序的顺序
//我这里是：首先按照年龄排序，然后是车的名字，最后是按照人的名字
NSArray *descriptorArray = [NSArray arrayWithObjects:personAgeDesc,carNameDesc,personNameDesc, nil];

NSArray *sortedArray = [array sortedArrayUsingDescriptors: descriptorArray];
NSLog(@"%@",sortedArray);
}

先按照age排序，如果age相同，按照car排序，如果car相同，按照name排序。 （注意：上面两种排序方法要想实现字符串显示，请重写description方法）