IB Action Functions

Any @IBAction function must:

• Include the sender object in its signature.
• Have its sender object being the specific type (e.g. UIButton, UITapGestureRecognizer, etc) and not AnyObject.
• Have its sender object being non-optional.
• Never be called directly from your code.

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Example

Good

@IBAction func doSomething(sender: UIButton) {
    // It's clear that this method is going to be called from an action caused by a UIButton.
}

Bad

@IBAction func doSomething() {
    // This method may be called from somewhere else in your code...
    // Inconsistency. Confusion. Not good.
}

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More complex example

Sometimes, there are scenarios where you need to perform the same action when pressing a button than when performing some action that's called from your code. In those cases, however, it's still good to separate concerns and encapsulate your action in a separated method, which will be called from both your @IBAction method and from somewhere else in your code.

Good

// MARK: - IBAction

@IBAction func doSomething(sender: UIButton) {
    self.performSomeAction()
}

// MARK: - Private

private func otherMethod() {
	self.performSomeAction()
}

private func performSomeAction() {
	// Perform the actual action
}

Bad

// MARK: - IBAction

@IBAction func doSomething() {
	// Not good that this method can be called from any other place which may have nothing to do with @IBAction
}

// MARK: - Private

private func otherMethod() {
	self.doSomething()	// bad
}

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Motivation

• Expressivity.
• Separation of concerns.
• It avoids confusions.