ios - 使用 UIAlertAction 快速增加标签栏角标(Badge)？
<p><pre><code>@IBAction func addToCart(sender: AnyObject) {
let itemObjectTitle = itemObject.valueForKey("itemDescription") as! String
let alertController = UIAlertController(title: "Add \(itemObjectTitle) to cart?", message: "", preferredStyle: .Alert)
let yesAction = UIAlertAction(title: "Yes", style: UIAlertActionStyle.Default) { (action) in
var tabArray = self.tabBarController?.tabBar.items as NSArray!
var tabItem = tabArray.objectAtIndex(1) as! UITabBarItem
let badgeValue = "1"
if let x = badgeValue.toInt() {
tabItem.badgeValue = "\(x)"
}
}
</code></pre>
<p>我不知道为什么我不能只做 += "(x)"</p>
<p>错误:
二元运算符“+=”不能应用于“字符串？”类型的操作数和'字符串'</p>
<p>我希望它在每次用户选择"is"时增加 1。现在显然它只是停留在 1。</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>您可以尝试访问 badgeValue 并将其转换为 Integer，如下所示:</p>
<p><strong> swift2</strong></p>
<pre><code>if let badgeValue = tabBarController?.tabBar.items?.badgeValue,
nextValue = Int(badgeValue)?.successor() {
tabBarController?.tabBar.items?.badgeValue = String(nextValue)
} else {
tabBarController?.tabBar.items?.badgeValue = "1"
}
</code></pre>
<p><strong>Swift 3 或更高版本</strong></p>
<pre><code> if let badgeValue = tabBarController?.tabBar.items?.badgeValue,
let value = Int(badgeValue) {
tabBarController?.tabBar.items?.badgeValue = String(value + 1)
} else {
tabBarController?.tabBar.items?.badgeValue = "1"
}
</code></pre>
<p>要删除角标(Badge)，只需将 nil 分配给 badgeValue 覆盖 viewDidAppear 方法:</p>
<pre><code>override func viewDidAppear(animated: Bool) {
tabBarController?.tabBar.items?.badgeValue = nil
}
</code></pre></p>
<p style="font-size: 20px;">关于ios - 使用 UIAlertAction 快速增加标签栏角标(Badge)？，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/40688008/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/40688008/
</a>
</p>
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