可以在iOS 7和iOS 8上运行的警报（Alert）

Question

可以在iOS 7和iOS 8上运行的警报（Alert）

11

当我尝试运行这个庞然大物时，出现了dyld: Symbol not found: _OBJC_CLASS_$_UIAlertAction。

我该如何弱化链接8.0的内容？

var device : UIDevice = UIDevice.currentDevice()!;
var systemVersion = device.systemVersion;
var iosVerion : Float = systemVersion.bridgeToObjectiveC().floatValue;
if(iosVerion < 8.0) {
    let alert = UIAlertView()
    alert.title = "Noop"
    alert.message = "Nothing to verify"
    alert.addButtonWithTitle("Click")
    alert.show()
} else {
    var alert : UIAlertController? = UIAlertController(title: "Noop", message: "Nothing to verify", preferredStyle: UIAlertControllerStyle.Alert)
    if alert {
        let actionStyle : UIAlertActionStyle? = UIAlertActionStyle.Default;
        var alertAction : UIAlertAction? = UIAlertAction(title: "Click", style: actionStyle!, handler: nil)
        if(alertAction) {
            alert!.addAction(alertAction)
            self.presentViewController(alert, animated: true, completion: nil)
        }
    }
}
return;

已解决：必须将UIKit标记为可选项而不是必需项。现在的简化版本是：

var device : UIDevice = UIDevice.currentDevice()!;
var systemVersion = device.systemVersion;
var iosVerion : Float = systemVersion.bridgeToObjectiveC().floatValue;
if(iosVerion < 8.0) {
    let alert = UIAlertView()
    alert.title = "Noop"
    alert.message = "Nothing to verify"
    alert.addButtonWithTitle("Click")
    alert.show()
} else {
    var alert : UIAlertController = UIAlertController(title: "Noop", message: "Nothing to verify", preferredStyle: UIAlertControllerStyle.Alert)
    alert.addAction(UIAlertAction(title: "Click", style:.Default, handler: nil))
    self.presentViewController(alert, animated: true, completion: nil)
}

- Anton Tropashko

可能是在Swift中显示UIAlertView的错误的重复问题。 - dibi

1

这是你所提到的问题的超集。其他人建议使用以下代码：

        let alert = UIAlertView()
        alert.title = "Noop"
        alert.message = "Nothing to verify"
        alert.addButtonWithTitle("Click")
        alert.show()

这对我有效。有人应该向苹果报告一个关于UIAlertView shim中方便初始化损坏的错误。 - Anton Tropashko

请查看我在这里发布的答案：https://dev59.com/xYDba4cB1Zd3GeqPD2c6#24091779 - Guy Kahlon

我做了。所提到的条目与UIAlertView初始化有关。我的条目与既拥有蛋糕又吃掉它有关。 - Anton Tropashko

"UIKit 必须标记为 Optional 而不是 Required 是什么意思？" - Bellots

链接阶段 -> 链接二进制文件与库，有硬链接和软链接开关（每个框架都有），将其从必需更改为可选（对于UIKit），以便该iOS不可知代码在动态链接器中加载时不会出错。 - Anton Tropashko

3个回答

3

在Xcode 6 beta 5中，由于Swift隐式链接框架，所以在"Link Phases -> Link Binary With Libraries"中没有任何内容。在这种情况下，您需要手动添加它，并将其标记为可选项。

此外，您可以仅检查UIAlertController的可用性，而无需明确检查系统版本。

if nil != NSClassFromString("UIAlertController") {
  //show alertcontroller
  ...
} else {
  //show alertview
  ...
}

- Alex

-1

尝试下面的 Objective C 代码。它适用于 iOS 8 及以下版本，运行良好。

if (IS_OS_8_OR_LATER) {
UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:title message:msg preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction *cancelAction = [UIAlertAction
                             actionWithTitle:@"OK"
                             style:UIAlertActionStyleCancel
                             handler:^(UIAlertAction *action)
                             {

                             }];
[alertVC addAction:cancelAction];

[[[[[UIApplication sharedApplication] windows] objectAtIndex:0] rootViewController] presentViewController:alertVC animated:YES completion:^{

}];
}
else{
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:msg delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
    [alert show];
}

- amitshinik

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- s4y · Accepted Answer

Explicitly add UIKit in the "Link Binary With Libraries" section of your project's build phases.

You can test for the existence of UIAlertController like this:

if NSClassFromString("UIAlertController") != nil {
    // Use it
} else {
    // Fall back
}

I wrote a wrapper that works on both iOS 7 and iOS 8. You can find it here. It takes a view controller followed by a bunch of optional arguments and any number of buttons:

showAlert(self, style: .ActionSheet, sourceView: cell, completion: {
    tableView.deselectRowAtIndexPath(indexPath, animated: true)
},
    (.Default, "Send clipboard", {
        if someCondition {
            // completion must be specified because of a Swift bug (rdar://18041904)
            showAlert(self, title: "Nothing to send", message: "The clipboard is empty.", completion: nil,
                (.Cancel, "OK", nil)
            )
        }
    }),
    (.Cancel, "Cancel", nil)
)