Instance Method

init

Implemented by subclasses to initialize a new object (the receiver) immediately after memory for it has been allocated.

Declaration

- (instancetype)init;

Return Value

An initialized object, or nil if an object could not be created for some reason that would not result in an exception.

Discussion

An init message is coupled with an alloc (or allocWithZone:) message in the same line of code:

SomeClass *object = [[SomeClass alloc] init];

An object isn’t ready to be used until it has been initialized.

In a custom implementation of this method, you must invoke super’s Initialization then initialize and return the new object. If the new object can’t be initialized, the method should return nil. For example, a hypothetical BuiltInCamera class might return nil from its init method if run on a device that has no camera.

- (instancetype)init {
    if (self = [super init]) {
        // Initialize self
    }
    return self;
}

In some cases, a custom implementation of the init method might return a substitute object. You must therefore always use the object returned by init, and not the one returned by alloc or allocWithZone:, in subsequent code.

The init method defined in the NSObject class does no initialization; it simply returns self. In terms of nullability, callers can assume that the NSObject implementation of init does not return nil.

See Also

Creating, Copying, and Deallocating Objects

+ alloc

Returns a new instance of the receiving class.

+ allocWithZone:

Returns a new instance of the receiving class.

- copy

Returns the object returned by copyWithZone:.

+ copyWithZone:

Returns the receiver.

- mutableCopy

Returns the object returned by mutableCopyWithZone: where the zone is nil.

+ mutableCopyWithZone:

Returns the receiver.

- dealloc

Deallocates the memory occupied by the receiver.

+ new

Allocates a new instance of the receiving class, sends it an init message, and returns the initialized object.