Key-Value Coding Programming Guide: Compliance Checklist

Compliance Checklist

Follow the steps summarized in this section to ensure your objects are key-value coding compliant. See the previous sections for details.

For each property that is an attribute or a to-one relationship:

Implement a method named <key> or is<Key>, or create an instance variable <key> or _<key>. The compiler typically does this for you when it automatically synthesizes properties.

Note

Although property names frequently begin with a lowercase letter, the default implementation of the protocol also works with names that begin with an uppercase letter, such as URL.
If the property is mutable, implement the set<Key>: method. The compiler typically does this for you when you allow it to automatically synthesize your properties.

Important

If you override the default setter, be sure not to invoke any of the protocol’s validation methods.
If the property is a scalar, override the setNilValueForKey: method to gracefully handle the case where a nil value is assigned to the scalar property.

For each property that is an ordered, to-many relationship (such as an NSArray object):

Implement a method named <key> that returns an array, or have an array instance variable named <key> or _<key>. The compiler typically does this for you when it automatically synthesizes properties.
Alternatively, implement the method countOf<Key> and one or both of objectIn<Key>AtIndex: and <key>AtIndexes:.
Optionally, implement get<Key>:range: to improve performance.

In addition, if the property is mutable:

Implement one or both of the methods insertObject:in<Key>AtIndex: and insert<Key>:atIndexes:.
Implement one or both of the methods removeObjectFrom<Key>AtIndex: and remove<Key>AtIndexes:.
Optionally, implement replaceObjectIn<Key>AtIndex:withObject: or replace<Key>AtIndexes:with<Key>: to improve performance.

For each property that is an unordered, to-many relationship (such as an NSSet object):

Implement the <key> that returns a set, or have an NSSet instance variable named <key> or _<key>. The compiler typically does this for you when it automatically synthesizes properties.
Alternatively, implement the methods countOf<Key>, enumeratorOf<Key>, and memberOf<Key>:.

In addition, if the property is mutable:

Opt in to validation for properties that need it:

Implement the validate<Key>:error: method, returning a boolean indicating the validity of the value, and a reference to an error object when appropriate.