ios - prepareForSegue 首先返回 nil
<p><p>我收到 <code>fatal error: unexpectedly found nil while unwrapping an Optional value</code> 当我从单元格中分离出来时。</p>
<p>代码如下:</p>
<pre><code>func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
if indexPath.section == 1 {
let listIngredients = recipeItem.ingredients
selectedIngredient = listIngredients.ingredient
}
tableView.deselectRowAtIndexPath(indexPath, animated: false)
performSegueWithIdentifier("showIngredientInRecipe", sender: self)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "showIngredientInRecipe" {
let svc = segue.destinationViewController as! UINavigationController
let destination = svc.topViewController as! IngredientDetailViewController
destination.ingredientItem = selectedIngredient
print("selectedIngredient \n \(selectedIngredient)")
}
}
</code></pre>
<p>这是我从调试器中得到的:</p>
<pre><code> selectedIngredient
nil
selectedIngredient
Optional(Ingredient {
name = Rye Whiskey;
inStock = 1;
type = IngredientType {
name = Spirit;
};
})
fatal error: unexpectedly found nil while unwrapping an Optional value
</code></pre>
<p>如您所见，<code>selectedIngredient</code> 打印了两次。第一次为 nil，第二次为预期内容。如果我将 <code>destination.ingredientItem = selectedIngredient</code> 替换为 <code>destination.ingredientItem = recipeItem.ingredients.ingredient</code> 则 segue 运行良好且没有错误。</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>您正在检查 indexPath 的部分是否为 1，如果不是，它仍将执行 segue。确保您的可选单元格位于第 1 节(或第 0 节？)并将您的 <code>performSegueWithIdentifier("showIngredientInRecipe", sender: self)</code> 调用移动到 if 语句以使其更安全。</p></p>
<p style="font-size: 20px;">关于ios - prepareForSegue 首先返回 nil，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/39186963/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/39186963/
</a>
</p>
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