ContainsValueForKey

ContainsValueForKey is a method name used in several programming frameworks to check whether a container or object has a value associated with a given key. It is most commonly seen in contexts that implement key-value coding (KVC) or dictionary-like collections. The exact behavior depends on the framework: in a dictionary, it typically returns true if the key exists and the corresponding value is not nil; in an object that supports KVC, it can indicate that the object exposes a value for that key and that such a value is not nil; in collections of records it may check whether at least one element provides a non-null value for that key.

In practice, the method is used to verify the presence of a value before performing operations that assume data availability. The semantics may vary: some implementations distinguish between the existence of a key and the presence of a non-null value, while others equate the two.

Example usage (pseudocode): if container.containsValueForKey("name") then proceed with name-dependent logic.

Because containsValueForKey is not universal, some frameworks provide alternatives such as containsKey:, hasValueForKey:, valueForKey:, or valueForKeyPath: to achieve similar checks. In many languages, presence and retrieval of values are handled by different methods, such as a direct key existence check or retrieving a value and testing whether it is nil or null.

See also: key-value coding, NSDictionary, NSManagedObject, containsKey, valueForKey, valueForKeyPath.