数组排序和过滤

排序

• NSComparator
  NSOrderedAscending 表示 obj1 应该排在 obj2 前面
  NSOrderedDescending 表示 obj2 应该排在 obj1 前面
  NSOrderedSame 表示 obj1 和 obj2 是一样的

[testArray sortUsingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {  
        if ([obj1 intValue] < [obj2 intValue]) {  
            return NSOrderedAscending;  
        }else if ([obj1 intValue] > [obj2 intValue]){  
            return NSOrderedDescending;  
        }else{  
            return NSOrderedSame;  
        }  
    }]; 

[testArray sortedArrayWithOptions:<#(NSSortOptions)#> usingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
        
    }]
NSSortConcurrent 是高效的但不稳定的排序算法,例如:快速排序
NSSortStable 是稳定的排序算法,例如:冒泡排序 插入排序
如果使用 NSSortStable 正确的结果是 @"one", @"two", @"four", @"three"
如果使用 NSSortConcurrent 正确的结果是 @"one", @"two", @"four", @"three" 或者 @"two", @"one", @"four", @"three"

• selector
  [[NSArray new] sortedArrayUsingSelector:<#(nonnull SEL)#>]
• function

[[NSArray new] sortedArrayUsingFunction:<#(nonnull NSInteger (*)(id  _Nonnull __strong, id  _Nonnull __strong, void * _Nullable))#> context:<#(nullable void *)#>];

• NSSortDescriptor

NSArray *firstNames = @[ @"Alice", @"Bob", @"Charlie", @"Quentin" ];
NSArray *lastNames = @[ @"Smith", @"Jones", @"Smith", @"Alberts" ];
NSArray *ages = @[ @24, @27, @33, @31 ];

NSMutableArray *people = [NSMutableArray array];
[firstNames enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    Person *person = [[Person alloc] init];
    person.firstName = [firstNames objectAtIndex:idx];
    person.lastName = [lastNames objectAtIndex:idx];
    person.age = [ages objectAtIndex:idx];
    [people addObject:person];
}];

NSSortDescriptor *firstNameSortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"firstName"
  ascending:YES
  selector:@selector(localizedStandardCompare:)];
NSSortDescriptor *lastNameSortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"lastName"
  ascending:YES
  selector:@selector(localizedStandardCompare:)];
NSSortDescriptor *ageSortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"age"
  ascending:NO];

NSLog(@"By age: %@", [people sortedArrayUsingDescriptors:@[ageSortDescriptor]]);
// "Charlie Smith", "Quentin Alberts", "Bob Jones", "Alice Smith"
NSLog(@"By first name: %@", [people sortedArrayUsingDescriptors:@[firstNameSortDescriptor]]);
// "Alice Smith", "Bob Jones", "Charlie Smith", "Quentin Alberts"
NSLog(@"By last name, first name: %@", [people sortedArrayUsingDescriptors:@[lastNameSortDescriptor, firstNameSortDescriptor]]);
// "Quentin Alberts", "Bob Jones", "Alice Smith", "Charlie Smith"

过滤

详情：http://nshipster.cn/nspredicate/

• NSPredicate

• NSCompoundPredicate

NSPredicate *compoundPredicate = [NSCompoundPredicate orPredicateWithSubpredicates:<#(nonnull NSArray<NSPredicate *> *)#>];
[NSCompoundPredicate andPredicateWithSubpredicates:<#(nonnull NSArray<NSPredicate *> *)#>]

• NSComparisonPredicate
  通过NSExpression生成predicate
• NSExpression
  如果我们仔细观察NSPredicate，我们会发现它NSPredicate实际上由更小的原子部分组成：两个NSExpressionS（左手值右手值），与操作者（例如相比<，IN，LIKE等等）。
  详情：http://nshipster.com/nsexpression/