Swift字典错误？ [英] Swift dictionary bug?

问题描述

所以我在Swift开始了一个项目，我来了这个问题：

So I started a project in Swift, and I've come to this problem:

这段代码的工作原理：

var dictionary = ["a":"valueOfA","b":"valueOfB","c":"valueOfC"]
println(dictionary)
dictionary["c"] = "newValOfC"
println(dictionary)

这不是：

var dictionary = [:]
dictionary = ["a":"valueOfA","b":"valueOfB","c":"valueOfC"]
println(dictionary)
dictionary["c"] = "newValOfC"
println(dictionary)

发送错误：

Playground execution failed: error: <REPL>:35:17: error: cannot assign to the result of this expression
dictionary["c"] = "newValC"
~~~~~~~~~~~~~~~ ^

请注意，这不是一个常数值

Notice that this is not a constant value

所以为什么不行

dictionary = ["a":"valueOfA","b":"valueOfB","c":"valueOfC"]

给出错误？

推荐答案

由于上下文没有提供足够的信息来推断该类型，您需要明确地将其命名为字典，否则swift假定它是一个 NSDictionary （我不清楚为什么。我假设更好的对象兼容性）：

Since the context does not provide enough information to infer the type, you'll need to explicitly name it as a dictionary, otherwise swift assumes it is an NSDictionary (I'm not clear on why though. I assume for better obj-c compatibility):

以下代码都可以正常工作：

The following code all works:

// Playground
import UIKit

var str:NSString = "Hello, playground"

var d0 = [:]
var d1: Dictionary = [:]

d0.setValue(UIWebView(), forKey: "asdf")

d1["asdf"] = 1
d1["qwer"] = "qwer"

这篇关于Swift字典错误？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！