FAQ: Structures - Mutating Methods

This community-built FAQ covers the “Mutating Methods” exercise from the lesson “Structures”.

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FAQs on the exercise Mutating Methods

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I’m at Mutating Methods and I’ve done all the other work (sometimes more than twice!) but I am needing clarification. Can anyone please explain init a bit better for me? (Sorry in advance! Inquiring minds just wanna know)

I’ve read it over and over and it FEELS like I am simply telling my program what it already knows. It SEEMS like an extra and wasted step. I’ve tried to understand using the original house/structure example… I’ll be finishing the next three lessons and probably pass the quiz, but I do not understand and (again :roll_eyes:) I have no idea how/why/where I would use this in a program.

If you are able to explain, perhaps use something other than what is already in the lesson? Here is a block from my lesson:

struct Dog {
  var age : Int
  var isGood : Bool

  init(age: Int, isGood: Bool) {
    self.age = age
    self.isGood = isGood
  }

  // birthday() is a mutating method:
  mutating func birthday() -> Int {
    print("Best doggy")
    self.age += 1
    return self.age
  }
}

Thank you. I promise, I have a very nice IQ, but I guess I need things written for 4 year olds, ha ha!

2 Likes

In this case, that init method is in fact a duplication of effort - it’s identical to the one that’s available by default.

The real usefulness of defining an init method would be if you wanted it to behave differently from the default implementation - say set some additional properties that aren’t passed in, or perhaps validate the arguments.