ios - 在 Swift 运行时确定实例是否具有可设置的属性

Question

我正在将旧代码移植到 Swift。我写了一个自定义输入 View ，它适用于我的某些自定义 View 。这是我用来附加输入 View 的便捷方法:

+ (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;
}

由于 UIView 的 inputView 是只读的，我必须检查传递给我的 View 是否可以设置输入 View 。我不知道我应该如何将标记的行移植到 Swift。如何检查传递的 View 是否将 inputView 声明为可设置？

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
}

Answer 1

Swift 确实提供了将字符串文字转换为Selector 数据类型的函数。可以这样写

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