ios - 错误 无法使用 'Dictionary<NSObject, AnyObject>' 类型的索引为 'String' 类型的值添加下标

Question

有人可以帮助我吗？我刚刚将我的小项目从 Objective-C 重新编程为 Swift，并收到以下错误:

Cannot subscript a value of type 'Dictionary' with an index of type 'String'

eins、zwei、drei 和 vier 是从另一个 View Controller 获取数据的字符串。

Objective-C 代码:

@property (strong, nonatomic) IBOutlet UISwitch *bluetoothSwitch;

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *SwitchState;
    NSArray *myStrings = [[NSArray alloc] initWithObjects:eins,zwei,drei, vier, nil];
    SwitchState = [myStrings componentsJoinedByString:mad:" | | "];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:mad:"store.plist"];

    NSFileManager *fileManager = [NSFileManager defaultManager];

    if (![fileManager fileExistsAtPath: path]) {
        path = [documentsDirectory stringByAppendingPathComponent: [NSString stringWithFormat:mad:"store.plist"] ];
    }

    NSMutableDictionary *savedValue = [[NSMutableDictionary alloc] initWithContentsOfFile: path];
    if ([[savedValue objectForKey:SwitchState] boolValue]) {
        self.bluetoothSwitch.on = [[savedValue objectForKey:SwitchState] boolValue];
    } else {
    }
}

我的 Swift 代码:

var eins = "Test"
var zwei = "Text"
var drei = "Test"
var vier = "Text"
var SwitchState = ""
let myStrings = [eins, zwei, drei, vier]
SwitchState = myStrings.joined(separator: " | | ")
let paths = NSSearchPathForDirectoriesInDomains(.applicationSupportDirectory, .userDomainMask, true)
let documentsDirectory = paths[0]
var path = URL(fileURLWithPath: documentsDirectory).appendingPathComponent("store.plist").absoluteString

let fileManager = FileManager.default

if !fileManager.fileExists(atPath: path) {
    path = URL(fileURLWithPath: documentsDirectory).appendingPathComponent("store.plist").absoluteString
}

var savedValue = NSDictionary(contentsOfFile: path) as Dictionary?
print("Das bekommt viewdid: \(SwitchState)")
if (savedValue?[SwitchState] as? NSNumber)?.boolValue ?? false {
    bluetoothSwitch.isOn = (savedValue?[SwitchState] as? NSNumber)?.boolValue ?? false
} else {
    print("nein")
}

这两行“产生”错误

if (savedValue?[SwitchState] as? NSNumber)?.boolValue ?? false {
    bluetoothSwitch.isOn = (savedValue?[SwitchState] as? NSNumber)?.boolValue ?? false

Answer 1

请不要尝试将 Objective-C 代码逐字翻译为 Swift。从 Swift 的角度来看，有很多很多不好的做法。

基本上不要使用NS... Swift 中的类(如果有 native 对应项)。

发生错误的原因是从 NSDictionary 进行桥接的结果至 Dictionary (不指定 Swift 类型)是 Dictionary<NSObject, AnyObject>与值类型 String 不兼容

这是一个真正的 Swift 版本:

let eins = "Test"
let zwei = "Text"
let drei = "Test"
let vier = "Text"
let myStrings = [eins, zwei, drei, vier]
let switchState = myStrings.joined(separator: " | | ")
let fileManager = FileManager.default
do {
    let applicationSupportDirectory = try fileManager.url(for: .applicationSupportDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
    let storeURL = applicationSupportDirectory.appendingPathComponent("store.plist")

    let data = try Data(contentsOf: storeURL)
    print("Das bekommt viewdid: \(switchState)")
    if let savedDictionary = try PropertyListSerialization.propertyList(from: data, format: nil) as? [String:Any],
        let savedState = savedDictionary[switchState] as? Bool {
        bluetoothSwitch.isOn = savedState
    } else {
        bluetoothSwitch.isOn = false
        print("nein")
    }
} catch { print(error) }

fileExists(atPath检查是多余的，所以我把它省略了。