条件绑定:if let error - 条件绑定的初始化程序必须具有可选类型

Conditional Binding: if let error – Initializer for conditional binding must have Optional type(条件绑定:if let error - 条件绑定的初始化程序必须具有可选类型)

问题描述

我正在尝试从我的数据源和以下代码行中删除一行:

I am trying to delete a row from my Data Source and the following line of code:

if let tv = tableView {

导致以下错误:

条件绑定的初始化器必须是 Optional 类型，而不是UITableView

Initializer for conditional binding must have Optional type, not UITableView

这里是完整的代码:

// Override to support editing the table view.
func tableView(tableView: UITableView, commitEditingStyle editingStyle:UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {

        // Delete the row from the data source

    if let tv = tableView {

            myData.removeAtIndex(indexPath.row)

            tv.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)

我应该如何更正以下内容?

How should I correct the following?

 if let tv = tableView {

推荐答案

if let/if var 可选绑定只在表达式右侧的结果时有效是可选的.如果右侧的结果不是可选的，则不能使用此可选绑定.此可选绑定的要点是检查 nil 并且仅在变量非 nil 时使用该变量.

if let/if var optional binding only works when the result of the right side of the expression is an optional. If the result of the right side is not an optional, you can not use this optional binding. The point of this optional binding is to check for nil and only use the variable if it's non-nil.

在您的情况下，tableView 参数被声明为非可选类型 UITableView.它保证永远不会是 nil.所以这里的可选绑定是不必要的.

In your case, the tableView parameter is declared as the non-optional type UITableView. It is guaranteed to never be nil. So optional binding here is unnecessary.

func tableView(tableView: UITableView, commitEditingStyle editingStyle:UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {
        // Delete the row from the data source
        myData.removeAtIndex(indexPath.row)
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)

我们所要做的就是摆脱 if let 并将其中所有出现的 tv 更改为仅 tableView.

All we have to do is get rid of the if let and change any occurrences of tv within it to just tableView.

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