一个数组内是对象类型.想根据对象内的属性进行排序.
很多人第一想到的是利用谓词.其实数组自带了一个更简便的方法便于我们进行排序
- (void)sortUsingComparator:(NSComparator NS_NOESCAPE)cmptr NS_AVAILABLE(10_6, 4_0);
举例.
定义一个 Person 对象
@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property(nonatomic,readwrite)int weight;
@end
使用方法
Person *person1 =[[Person alloc]init];
Person *person2 =[[Person alloc]init];
Person *person3 =[[Person alloc]init];
person1.weight =1;
NSMutableArray *array =[[NSMutableArray alloc]init];
[array addObject:person1];
person2.weight =3;
[array addObject:person2];
person3.weight =2;
[array addObject:person3];
for (Person *p in array) {
NSLog(@"排序前%d",p.weight);
}
[array sortUsingComparator:^NSComparisonResult(Person *obj1, Person *obj2) {
return [@(obj1.weight) compare:@(obj2.weight)];
}];
for (Person *p in array) {
NSLog(@"排序后%d",p.weight);
}
打印日志为:
2017-05-27 17:20:51.382 Demo[18726:662926] 排序前1
2017-05-27 17:20:51.383 Demo[18726:662926] 排序前3
2017-05-27 17:20:51.383 Demo[18726:662926] 排序前2
2017-05-27 17:20:51.383 Demo[18726:662926] 排序后1
2017-05-27 17:20:51.383 Demo[18726:662926] 排序后2
2017-05-27 17:20:51.383 Demo[18726:662926] 排序后3
是不是感觉很方便?所以多看看系统定义的方法对我们提高效率非常有用
另外分享一些常用 OC 排序方法:
1).不可变数组
- (NSArray *)sortedArrayUsingSelector:(SEL)comparator;
- (NSArray *)sortedArrayUsingComparator:(NSComparator)cmptr;
2)可变数组
- (void)sortUsingSelector:(SEL)comparator;
- (void)sortUsingComparator:(NSComparator)cmptr;
3).字典排序
- (NSArray *)keysSortedByValueUsingComparator:(NSComparator)cmptr
- (NSArray *)keysSortedByValueUsingSelector:(SEL)comparator;
1).不可变数组排序:(方法1)
NSArray *arr = @[@"aa",@"rr",@"pp",@"hh",@"xx",@"vv"];
//用系统的方法进行排序,系统缺少两个元素比较的方法.
//selector方法选择器.
NSArray *sortArr = [arr sortedArrayUsingSelector:@selector(compare:)];
NSLog(@"%@",sortArr);
方法2:block块语法
[arr sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
return [(NSString *)obj1 compare:(NSString *)obj2];
}];
NSLog(@"%@",arr);
}
2).可变数组排序:方法1
NSMutableArray *arr = [@[@54 ,@33,@12,@23,@65] mutableCopy];
[arr sortUsingSelector:@selector(compare:)];//compare数组中两个元素比较的方法
NSLog(@"%@",arr);
方法2
[arr sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
return [(NSNumber *)obj1 compare:(NSNumber *)obj2];
}];
NSLog(@"%@",arr);
}
注:字典方法类似
例题:定义一个学生对象,对学生对象按照,姓名,年龄,成绩,学号进行排序,(两种排序方式)
方法1:(用selector方法选择器,需要重新定义comparator)
代码如下:
1.对象声明(student.h中)
@property (nonatomic, retain) NSString *name;
@property (nonatomic, assign) NSInteger age;
@property (nonatomic, assign) CGFloat score;
@property (nonatomic, assign) NSInteger number;
//初始化
- (id)initWithName:(NSString *)name age:(NSInteger)age score:
(CGFloat)score number:(NSInteger)number;
//便利构造器
+ (id)studentWithName:(NSString *)name age:(NSInteger)age score:
(CGFloat)score number:(NSInteger)number;
//两个学生按照年龄比较的方法
- (NSComparisonResult)compareByAge:(Student *)stu;
//两个学生按照姓名比较的方法
- (NSComparisonResult)compareByName:(Student *)stu;
//两个学生按照成绩比较的方法
- (NSComparisonResult)compareByScore:(Student *)stu;
//两个学生按照学号比较的方法
- (NSComparisonResult)compareByNumber:(Student *)stu;
2.实现(student.m文件)
- (id)initWithName:(NSString *)name age:(NSInteger)age score:
(CGFloat)score number:(NSInteger)number {
self = [super init];
if (self != nil) {
self.name = name;
self.age = age;
self.score = score;
self.number = number;
}
return self;
}
//便利构造器
+ (id)studentWithName:(NSString *)name age:(NSInteger)age score:
(CGFloat)score number:(NSInteger)number {
Student *student = [[Student alloc] initWithName:name
age:age score:score number:number];
return student;
}
//重写description
- (NSString *)description {
return [NSString stringWithFormat:
@"name:%@,age:%ld,socre:%.1f,number:%ld",
self.name, self.age, self.score, self.number];
}
//两个学生按照年龄比较的方法
- (NSComparisonResult)compareByAge:(Student *)stu {
return [@(self.age) compare:@(stu.age)];//或者下面方法
//return self.age > stu.age ? NSOrderedDescending
: self.age == stu.age ? NSOrderedSame : NSOrderedAscending;
}
//两个学生按照姓名降序的方法
- (NSComparisonResult)compareByName:(Student *)stu {
return - [self.name compare:stu.name];
}
//两个学生按照成绩降序比较的方法
- (NSComparisonResult)compareByScore:(Student *)stu {
return -[@(self.score) compare: (stu.score)];
//return self.score < stu.score ? NSOrderedDescending :
self.score == stu.score ? NSOrderedSame : NSOrderedAscending;
}
//两个学生按照学号升序的方法
- (NSComparisonResult)compareByNumber:(Student *)stu {
return [@(self.number) compare: (stu.number)];
//return self.number > stu.number ? NSOrderedDescending
: self.number == stu.number ? NSOrderedSame : NSOrderedAscending;
}
主函数(main.h)
Student *student1 = [Student studentWithName:@"a" age:23 score:21 number:3434343];
Student *student2 = [Student studentWithName:@"b" age:45 score:432.4 number:324];
Student *student3 = [Student studentWithName:@"c" age:32 score:4321.4 number:2343];
Student *student4 = [Student studentWithName:@"d" age:7 score:43.4 number:233];
Student *student5 = [Student studentWithName:@"e" age:73 score:65 number:2332424];
NSMutableArray *arr = [NSMutableArray arrayWithObjects:
student1,student2,student3,student4,student5,nil];
//按照年龄升序排序
[arr sortUsingSelector:@selector(compareByAge:)];
NSLog(@"%@",arr);
//按照成绩降序排序
[arr sortUsingSelector:@selector(compareByScore:)];
NSLog(@"%@",arr);
//按照姓名降序排序
[arr sortUsingSelector:@selector(compareByName:)];
NSLog(@"%@",arr);
//按照学号升序排序
[arr sortUsingSelector:@selector(compareByNumber:)];
NSLog(@"%@",arr);
方法2.用block块语法进行排序
//按年龄升序排序
[arr sortUsingComparator:^(id obj1,id obj2) {
return [@(((Student *)obj1).age) compare: @(((Student *)obj2).age)];
}];
NSLog(@"%@",arr);
//按成绩降序排序
[arr sortUsingComparator:^(id obj1,id obj2) {
return [@(((Student *)obj1).score) compare: @(((Student *)obj2).score)];
}];
NSLog(@"%@",arr);
//按姓名降序排序
[arr sortUsingComparator:^(id obj1,id obj2) {
return -[[(Student *)obj2 name] compare: [(Student *)obj1 name]];
}];
NSLog(@"%@",arr);
//按学号升序排序
NSComparator sortBlock = ^(id obj1,id obj2) {
return [@(((Student *)obj1).number) compare: @(((Student *)obj2).number)];
};
[arr sortUsingComparator:sortBlock];
NSLog(@"%@",arr);
