Beginning Table Views · Creating a Model | Ray Wenderlich

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This is a companion discussion topic for the original entry at https://www.raywenderlich.com/5995-beginning-table-views/lessons/14
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What is the purpose of initializer?
In the ios tutorial about the bull’s eye app, it does not require that initializer.
If we use some model, that is mandatory?

3

@bdmoakley Can you please help with this when you get a chance? Thank you - much appreciated! :]

4

The initializer allows us to setup values for an object when the object is created. In this case, we create a few objects that will use to populate the data. I hope that helps!

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Hi, could you please explain the required init ?(coder aDecoder: NSCoder) {

todoList = TodoList()

super .init(coder: aDecoder)

}

What is this and why do we need it?
This is called when this view controller is initialised from the storyboard. I don’t really understand it…
Is this an initialiser method that is called when the user is allowed to fill in a tableview ie Checklist (customise it) with his own list? So basically all table view would have this initialiser method?
Many Thanks in advance

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This method is called when the storyboard creates an instance of the view controller, so that’s a good place to do some initialization. There are other places you can initialize your objects as well. And yes, a table view does have this initializer as well.

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Thank you for your answer, Brian. Can I please ask you if you have this method NSCoder in the iOS APPRENTICE BOOK, particularly for this app? Is it included in the code ?

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Brian,

Please, how is it possible that the same app in the book does not contain the below code anywhere? It is not in the book… Checklist app. I wanted to look up this part to read more about it…

required init?(coder aDecoder: NSCoder) {
super.init()
}

override init() {
super.init()
}

9

Hey there,

When we created these video tutorials, we started with the iOS Apprentice and ultimately the app evolved from there. This is why there is a difference. If you are curious about NSCoding, you can check out this tutorial over here:

https://www.raywenderlich.com/6733-nscoding-tutorial-for-ios-how-to-permanently-save-app-data

Feel free to shoot me any questions if you have them

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I have a question when we create the variable “row0Item”. It is first created as a CheckListItem type. Then it is set as a base CheckListItem class through the initializer.

var row0Item: CheckListItem

required init?(coder aDecoder: NSCoder) {
    row0Item = CheckListItem()
    row0Item.name = "Take a jog"
    super.init(coder: aDecoder)
}

Why would we not just set it as a base CheckListItem class to begin with? i.e.

var row0Item = CheckListItem()

required init?(coder aDecoder: NSCoder) {
    row0Item.name = "Take a jog"
    super.init(coder: aDecoder)
}

Is this a best practice/matter of preference or is there a reason we would prefer to first declare its type then set it equal to a base class in the initializer?

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@bdmoakley Can you please help with this when you get a chance? Thank you - much appreciated! :]

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Apple lays out the best practice in their Swift programming guide. Essentially, if the property will always start with the same initial value, then use a default property. You can find out more over here:

https://docs.swift.org/swift-book/LanguageGuide/Initialization.html

Look under the section titled Default Property Values. I hope that helps!

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That does help, thank you!

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What does super.init(coder: aDecoder) do?

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@ericsutton33 Please check out this article when you get a chance:

I hope it helps!

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Why do we need row0Item.checked = !row0Item.checked and what does it do exactly? I thought that the code below would change the state of the check:

if indexPath.row == 0 {
if row0Item.checked {
cell.accessoryType = .none
} else {
cell.accessoryType = .checkmark
}

1 Like
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I have the same question.
Could you please kindly explain why row0Item.checked = !row0Item.checked is needed in addition to the code below?

if indexPath.row == 0 {
if row0Item.checked {
cell.accessoryType = .none
} else {
cell.accessoryType = .checkmark
}

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This code changes the checkmark data to point to the opposite of its current state.

row0Item.checked = !rowOItem.checked

This means that if the checked property is true, it is now false. If it’s false, it’s now true.

This code here:

if row0Item.checked {
    cell.accessoryType = .none
} else {
    cell.accessoryType = .checkmark
}

This updates the tableview based on the checked property. This code visually adds the checkmark.

Whenever you run into a question about what a certain line of code does, try deleting it and see the results.

In any case, I hope my explanation helps.

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Hi Brian,

Thank you for the follow up.

Is it fair to say that row0Item.checked = !rowOItem.checked is related to tableview datasource and if row0Item.checked {
cell.accessoryType = .none
} else {
cell.accessoryType = .checkmark
}
is linked to the tableview delegate method?

Sincerely, Joey.

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@bdmoakley Can you please help with this when you get a chance? Thank you - much appreciated! :]