ContainsObject: returns NO when isEqual and hash match

Question

I have an NSMutableOrderedSet from which I add and remove MTLModels. The hash and isEqual methods will return true for two objects, but containsObject will return false.

Sometimes this code works, and sometimes not.

models count: 1
isEqual: 1
hashes equal: 1
containsObject: 0

How is this possible, the code below can print above?

@property (nonatomic, strong) NSMutableOrderedSet *models;

- (void)remove:(MTLModel *)model {
  NSLog(@"models count: %d", self.models.count);
  MTLModel *modelInSet = (MTLModel *)self.models.firstObject;
  NSLog(@"isEqual: %d", [modelInSet isEqual:model]);
  NSLog(@"hashes equal: %d", modelInSet.hash == model.hash);
  NSLog(@"containsObject: %d", [self.models containsObject:model]);
}

Update:

YES is returned as a continuation when NSMutableOrderedSet returns NO:

[[self.models array] containsObject:model]

Update 2:

If I check to see if modelInSet is contained in self.models, this also returns NO, even if it is the object returned by firstObject.

Answer 1

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