[iOS/WebKit] Completion handler passed to [webView:decidePolicyForNavigationAction:decisionHandler:] was called more than once 오류

오류

다른 ViewController에서 동시에 한 개의 webView를 사용하고 있던 중 아래 오류가 발생하였다.

Completion handler passed to [webView:decidePolicyForNavigationAction:decisionHandler:] was called more than once

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원인

webView에서 decideHandler나 completionHandler의 호출은 한 번 밖에 되지 않는다.

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해결

CompletionHandlerWrapper Class를 선언하여 webView에 적용

class CompletionHandlerWrapper<Element> {
  private var completionHandler: ((Element) -> Void)?
  private let defaultValue: Element

  init(completionHandler: @escaping ((Element) -> Void), defaultValue: Element) {
    self.completionHandler = completionHandler
    self.defaultValue = defaultValue
  }

  func respondHandler(_ value: Element) {
    completionHandler?(value)
    completionHandler = nil
  }

  deinit {
    respondHandler(defaultValue)
  }
}

 func webView(_ webView: WKWebView, runJavaScriptConfirmPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping (Bool) -> Void) {
    let completionHandlerWrapper = CompletionHandlerWrapper(completionHandler: completionHandler, defaultValue: false)
    let alertController = UIAlertController(title: message, message: nil, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "확인", style: .default) { _ in completionHandlerWrapper.respondHandler(true) })
    alertController.addAction(UIAlertAction(title: "취소", style: .cancel) { _ in completionHandlerWrapper.respondHandler(false) })
    present(alertController, animated: true, completion: nil)
  }

 

 

출처

WKWebView의 UIDelegate completion crash 해결하기

 

[ios] Completion handler passed to -[Connect.MainViewController webView:decidePolicyForNavigationAction:decisionHandler:] was ca