Swift Overload init ()

Question

i will overload the init method in Swift, how can I implement this?

here is my code that doesn't work

code removed

Edit:

So this will work fine

override init() { super.init(); } init(title:String?) { super.init(); self.title = title } convenience init(title:String?, imageName:String?) { self.init(title:title) self.imageName = imageName } convenience init(title:String?, imageName:String?, contentKey:String?) { self.init(title:title, imageName:imageName) self.contentKey = contentKey } 

Answer 1

I connected the sample to the playground, here is how I got it to work:

 class Y { } class X : Y { var title: String? var imageName: String? override init() { } init(aTitle:String?) { super.init() self.title = aTitle } convenience init(aTitle:String?, aImageName:String?) { self.init(aTitle: aTitle) self.imageName = aImageName } } 

• init(aTitle:String?, aImageName:String?) cannot call init(aTitle:) and still be a designated initializer, it must be a convenience initializer.
• self.init must be before anything else in init(aTitle:String?, aImageName:String?) .
• The initializer must be passed the parameter name self.init(aTitle) must be self.init(aTitle: aTitle) .

As a side note, I removed the unnecessary semicolons and put super.init() first for style reasons.

Hope this helps.

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UPDATE

To follow Apple's recommendations, there should be only one assigned, the rest should be convenience initializers. For example, if you decide that init(aTitle:String?) Should be the designated initializer, then the code should look like this:

 convenience override init() { self.init(aTitle: nil) // A convenience initializer calls the designated initializer. } init(aTitle:String?) { super.init() // Only the designated initializer calls super.init. self.title = aTitle } convenience init(aTitle:String?, aImageName:String?) { self.init(aTitle: aTitle) // A convenience initializer calls the designated initializer. self.imageName = aImageName } 

Sometimes you may need to have more than one assigned initializer, such as a UIView , but this should be the exception, not the rule.

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UPDATE 2

Classes must have one designated initializer. The convenience initializer (in the end) will invoke the designated initializer.

Initialization

A class can have multiple initializers. This happens when the initialization data can take various forms or when some initializers provide default values ​​as a convenience. In this case, one of the initialization methods is called the designated initializer , which fully fulfills the initialization parameters.

Multiple Initializers

Assigned Initializer

A class initializer that accepts a full set of initialization parameters is usually a designated initializer. The designated initializer of the subclass must invoke the designated initializer of its superclass by sending a super message. Convenience initializers (or secondary), which may include init-do not super. Instead, they call (via a message to themselves) the initializer in a series with the following most parameters, providing a default value for the parameter not passed to it. The final initializer in this series is the designated initializer.