CODEWITHSUNDEEP
swiftgetsetprotocols
陳香君
陳香君

Reputation: 39

Why I can change the get-only property?

Can anyone explain why I can set value to a get-only property?

Here is the example. This protocol contains get-only property of type the custom class, and a class conform to it.

protocol ViewModel {
    var title: MyTitle { get }
}

class MyTitle {
    var title: String
    var otherProperty: Int
}

class MyViewModel: ViewModel {
    var title: MyTitle
    init() {
        self.title = MyTitle.init()
    }
    func didChangeTitle(title: String) {
        self.title.title = title
    }
}

I think the title property should be get-only, and will trigger function in MyViewModel when user finish editing UITextView.


class TableViewCell: UITableViewCell, UITextViewDelegate {
    var viewModel: MyViewModel?
    func bind(to viewModel: MyViewModel) {
        self.viewModel = viewModel
    }

    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        if text == "\n" {
            self.viewModel?.title.title = textView.text /* Why can the property supposed to be get-only be changed here */
            textView.resignFirstResponder()
            return false
        }
        return true
    }
}

But actually I can update the value directly without the function of MyViewModel.

Can anyone explain?

Upvotes: 0

Views: 559

Answers (1)

iamin
iamin

Reputation: 76

You are not actually declaring a get-only property by conforming a protocol. You can use computed property, and declare it by

var title: String {
    return "Something"
}

And furthermore, you are changing a property inside a class, not that class itself

EDIT

Or as proposed in the comments you can define a private setter private (set) var title: String

Upvotes: 1

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