pragma mark 数组排序1

NSArray *array = [NSArray arrayWithObjects:@"2", @"3", @"1", @"4", nil nil];  
  
// 返回一个排好序的数组，原来数组的元素顺序不会改变  
// 指定元素的比较方法：compare:  
NSArray *array2 = [array sortedArrayUsingSelector:@selector(compare:)];  
NSLog(@"array2:%@", array2);  

pragma mark 数组排序2

Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];  
Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];  
Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];  
Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];  
NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];  
// 指定排序的比较方法  
NSArray *array2 = [array sortedArrayUsingSelector:@selector(compareStudent:)];  
NSLog(@"array2:%@", array2);  

}

• (NSComparisonResult)compareStudent:(Student *)stu {
  // 先按照姓排序
  NSComparisonResult result = [self.lastname compare:stu.lastname];
  // 如果有相同的姓，就比较名字
  if (result == NSOrderedSame) {
  result = [self.firstname compare:stu.firstname];
  }
  return result;

pragma mark 数组排序3

Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];  
Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];  
Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];  
Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];  
NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];  
  
// 利用block进行排序  
NSArray *array2 = [array sortedArrayUsingComparator:  
 ^NSComparisonResult(Student *obj1, Student *obj2) {  
     // 先按照姓排序  
     NSComparisonResult result = [obj1.lastname compare:obj2.lastname];  
     // 如果有相同的姓，就比较名字  
     if (result == NSOrderedSame) {  
         result = [obj1.firstname compare:obj2.firstname];  
     }  
       
     return result;  
}];  
  
NSLog(@"array2:%@", array2);  

pragma mark 数组排序4-高级排序

Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li" bookName:@"book1"];  
Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang" bookName:@"book2"];  
Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li" bookName:@"book2"];  
Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao" bookName:@"book1"];  
NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];  
  
// 1.先按照书名进行排序  
// 这里的key写的是@property的名称  
NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"book.name" ascending:YES];  
// 2.再按照姓进行排序  
NSSortDescriptor *lastnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"lastname" ascending:YES];  
// 3.再按照名进行排序  
NSSortDescriptor *firstnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"firstname" ascending:YES];  
// 按顺序添加排序描述器  
NSArray *descs = [NSArray arrayWithObjects:bookNameDesc, lastnameDesc, firstnameDesc, nil nil];  
  
NSArray *array2 = [array sortedArrayUsingDescriptors:descs];  
  
NSLog(@"array2:%@", array2);