CODEWITHSUNDEEP
iosobjective-cswiftintrospection
duci9y
duci9y

Reputation: 4168

Determine if instance has settable property during runtime in Swift

I am porting old code to Swift. I wrote a custom input view, which works with certain custom views of mine. Here's the convenience method I use to attach the input view:

+ (POGramophoneView *)attachToView:(UIView *)view delegate:(id)delegate
{
    if ([view.inputView isKindOfClass:self]) return (POGramophoneView *)view.inputView;

    POGramophoneView *gramophone = [[POGramophoneView alloc] initWithFrame:CGRectMake(0, 0, 1024, 267)];

    gramophone.attachedView = view;

    NSAssert([view respondsToSelector:@selector(setInputView:)], @"Gramophone view %@ cannot attach to %@ because it does not respond to setInputView:", gramophone, view);

    // This line
    [view performSelector:@selector(setInputView:) withObject:gramophone];

    [view reloadInputViews];

    return gramophone;
}

Since inputView of UIView is readonly, I have to check if the view passed to me can have an input view set. I don't know how I should port the marked line to Swift. How do I check if the passed view has inputView declared as settable?

class func attachToView(view: UIView, delegate: POGramophoneViewDelegate) -> POGramophoneView {
    if view is POGramophoneView {
        return view
    }

    var gramophone = POGramophoneView(frame: CGRectMake(0, 0, 1024, 267))
    gramophone.attachedView = view

    // set inputview to new gramophone
    view.reloadInputViews()

    return gramophone
}

Upvotes: 1

Views: 1350

Answers (1)

Gandalf
Gandalf

Reputation: 2417

Swift does provide function to convert a string literal into Selector data type. You can write it like this

if view.respondsToSelector(Selector("setInputView:")) {
    // To call the selector use KVO technique.
    view.setValue(gramophone, forKey:"inputView");
}

Upvotes: 1

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