可在iOS 7和iOS 8上运行的警报 [英] Alert that can work on iOS 7 and iOS 8

问题描述

我正在得到dyld：未找到符号：_OBJC_CLASS _ $ _ UIAlertAction
当我试图让这个怪物运行时。

I'm getting dyld: Symbol not found: _OBJC_CLASS_$_UIAlertAction when I'm trying to get this monstrosity to run.

我如何弱连接8.0东西？

How do I weaklink 8.0 stuff?

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：UIKit必须标记为Optional而不是Required。简化版现在是：

Resolved: UIKit had to be marked Optional rather than Required. Simplified version is now:

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)
}

推荐答案

• 在项目构建阶段的Link Binary With Libraries部分中明确添加UIKit。

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

    您可以测试UIAlertController的存在，如下所示：

    You can test for the existence of UIAlertController like this:

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

  
  

  • 我写了一个包装器适用于iOS 7和iOS 8.您可以在此处找到它。它需要一个视图控制器，后跟一堆可选参数和任意数量的按钮：

  • 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)
    )
    

  
  

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