switch 语句的 default case 是否调用了先前的 case？

Question

Whenever I use a switch-case statement – 9 times out of 10 – the final default case is almost always that of a case above it.

ie.

// WebView Observers
switch webView {
    case webView:
        webViewURLObserver = webView.observe(\.url, options: .new) { [weak self] webView, change in
            let url = "\(String(describing: change.newValue))"
            self?.urlDidChange(urlString: url) }
    case customizerWebView:
        customizerURLObserver = customizerWebView.observe(\.url, options: .new) { [weak self] webView, change in
            let url = "\(String(describing: change.newValue))"
            self?.customizerURLDidChange(urlString: url) }
    case default:
        webViewURLObserver = webView.observe(\.url, options: .new) { [weak self] webView, change in
        let url = "\(String(describing: change.newValue))"
        self?.urlDidChange(urlString: url) }
    }

Is there a way to have the default case just reference one of the already-existing cases?

// What I'm trying to accomplish
switch webView {
    case webView:
        [webView Observer Code]
        ...
    case customizerWebView:
        [customizerWebView Observer Code]
        ...
    case default:
        switch.case = webView || switch.case = 0
    }

Answer 1

A possible solution is to use fallthrough .

Instead of thinking:

In case of "default": do something of target case

Think it in the other way:

In case of target case, do "default".

switch webView {
case customizerWebView:
    customizerURLObserver = customizerWebView.observe(\.url, options: .new) { [weak self] webView, change in
        let url = "\(String(describing: change.newValue))"
        self?.customizerURLDidChange(urlString: url) }
case webView:
        fallthrough
case default:
    webViewURLObserver = webView.observe(\.url, options: .new) { [weak self] webView, change in
    let url = "\(String(describing: change.newValue))"
    self?.urlDidChange(urlString: url) }
}

Or as, pointed by @xTwiteDx , you can remove the lines case webView: fallthrough if you don't do a specific code before fallthrough . It's up to you, how you are comfortable with you code, how to explicit or not cases.