无法将 Float 类型的值转换为预期的参数类型 NSNumber

Question

我正在从 swift 类调用目标 c 中的一个方法。我的目标 c 方法期望 NSNumber 格式的数字。我没有在 swift 中定义数字类型，但我仍然收到以下消息。有没有办法解决这个问题？

- (void)getPercentageMatch:(NSString *)answer listOfAnswers:(NSArray *)validAnswers completionBlock:(void(^)(BOOL isSuccess, NSNumber *percent))completionBlock {
NSMutableDictionary *params = [NSMutableDictionary dictionary];
[params setValue:answer forKey:@"myanswer"];
[params setValue:validAnswers forKey:@"answers"];
NSMutableURLRequest *req = [AuthorizationHandler createAuthReq:@"POST" path:@"validateAnswer" params:params];

AFJSONRequestOperation *op = [[AFJSONRequestOperation alloc] initWithRequest:req];
[op setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSDictionary *responseheaders = (NSDictionary *)responseObject;
    if (completionBlock) {
        completionBlock(true, [responseheaders valueForKey:@"percentage"]);
    }
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    if (completionBlock) {
        completionBlock(false, 0);
    }
}];
[op start];
return;
}

我还强制完成块类型转换

as! completionBlock(Bool, NSNumber)

但这不起作用。

我是 swift 新手，任何教程/指针将不胜感激 :)

编辑 1：

当我修改完成块时

let completionBlock = { (isSuccess, percent) in
        print("-------", isSuccess, percent)
    }
    MTRestkitManager.instance().getPercentageMatch(_:text, listOfAnswers:validAnswers, completionBlock:completionBlock)

我没有收到任何错误。但是，如果我再次添加一个轻微的修改，我会得到一个错误。

为什么行为会改变？

编辑 2： 按照科林的解决方案，做了如下改动

    @IBAction func submitButtonTapped(_ sender: Any) {
    answerTextView.resignFirstResponder()
    if answerTextView.textColor == UIColor.lightGray {
        ZUtility.showError(NSLocalizedString("Please enter answer before submitting", comment: ""))
        return;
    }
    if answerTextView.text.isEmpty {
        ZUtility.showError(NSLocalizedString("Please enter answer before submitting", comment: ""))
        setPlaceholderText()
        return;
    }
    let text = answerTextView.text as String
    let completionBlock = { (isSuccess, percent:NSNumber) -> (Void) in
        self.handleAnswer(isSuccess: isSuccess, percent: Float(percent))
    }
    MTRestkitManager.instance().getPercentageMatch(_:text, listOfAnswers:validAnswers, completionBlock:completionBlock)
}

在最后一行我收到一个错误：无法将类型 '(Bool, NSNumber) -> (Void)' 的值转换为预期的参数类型 '((Bool, NSNumber?) -> (Void)!'

Answer 1

显然，Float 是从self 的handleAnsewer() 函数推断出来的。您应该手动在 completionBlock 中定义正确的类型：

let completionBlock = { (isSuccess, percent: NSNumber?) in
    self.handleAnsewer(isSuccess: isSuccess, percent: percent.floatValue ?? 0)
}

请记住，您不能在 Swift 中自动进行类型转换，您应该调用显式初始化器，例如 NSNumber(value: myFloat) 或 Int(percent。

附：我打赌你来自 python :)