ios - 'NSDictionary ?' is not convertible to ' NSCopying'

Question

我正在尝试将以下代码转换为 Swift

- (id)init {
    self = [super init];

    if (self) {
        // Fetch Current Configuration
        NSBundle *mainBundle = [NSBundle mainBundle];
        self.configuration = [[mainBundle infoDictionary] objectForKey:@"Configuration"];

        // Load Configurations
        NSString *path = [mainBundle pathForResource:@"Configurations" ofType:@"plist"];
        NSDictionary *configurations = [NSDictionary dictionaryWithContentsOfFile:path];

        // Load Variables for Current Configuration
        self.variables = [configurations objectForKey:self.configuration];
    }

    return self;
}

这是 Swift 版本:

private var configuration: String?
private var properties: NSDictionary?

init() {
    println("Load configurations")
    let mainBundle = NSBundle.mainBundle()
    self.configuration = mainBundle.infoDictionary?["Configuration"] as? String

    let path = mainBundle.pathForResource("Configurations", ofType: "plist")

    var configurations = NSDictionary(contentsOfFile: path!)
    self.properties = configurations[configuration!] as? NSDictionary
}

但是最后一行给了我两个编译错误:

Configuration.swift:25:27: 'NSDictionary?' is not convertible to 'NSCopying'
Configuration.swift:25:14: Cannot assign to immutable value of type 'NSDictionary?'

我尝试了对代码进行各种修改，as!、NSMutableDictionary 等。但就是无法编译。有什么建议吗？

Answer 1

您的 configurations 字典是可选的，因此您必须在使用时打开它，因此请替换此行:

self.properties = configurations[configuration!] as? NSDictionary

用这一行:

self.properties = configurations![configuration!] as? NSDictionary

您需要在使用可选词典时添加!。

或者你可以使用安全的 if let 来做到这一点:

if let config = configurations![configuration!] as? NSDictionary {
   self.properties = config
}