尝试访问字典时出现 Swift 错误 : `Could not find member ' subscript'`

Question

这不会编译: 我尝试了几种不同的方法；声明字典的不同方式，更改其类型以匹配数据的嵌套性。我还尝试明确地说我的 Any 是一个集合，因此它可以被下标。没有骰子。

import UIKit


import Foundation

class CurrencyManager {

    var response = Dictionary<String,Any>()
    var symbols = []


    struct Static {
        static var token : dispatch_once_t = 0
        static var instance : CurrencyManager?
    }

    class var shared: CurrencyManager {
        dispatch_once(&Static.token) {  Static.instance = CurrencyManager() }
        return Static.instance!
    }

    init(){
        assert(Static.instance == nil, "Singleton already initialized!")
        getRates()

    }


    func defaultCurrency() -> String {

        let countryCode  = NSLocale.currentLocale().objectForKey(NSLocaleCountryCode) as String
        let codesToCountries :Dictionary = [ "US":"USD" ]

        if let localCurrency = codesToCountries[countryCode]{
            return localCurrency
        }

        return "USD"

    }

    func updateBadgeCurrency() {

        let chanCurr = defaultCurrency()

        var currVal :Float = valueForCurrency(chanCurr, exchange: "Coinbase")!

        UIApplication.sharedApplication().applicationIconBadgeNumber = Int(currVal)

    }

    func getRates() {
        //Network code here
        valueForCurrency("", exchange: "")
    }

    func valueForCurrency(currency :String, exchange :String) -> Float? {
        return response["current_rates"][exchange][currency] as Float
    }


}

Answer 1

我们来看看

response["current_rates"][exchange][currency]

response声明为 Dictionary<String,Any>() ，因此在第一个下标之后，您尝试在 Any 类型的对象上调用另外两个下标。

解决方案 1. 将响应类型更改为嵌套字典。请注意，我添加了问号，因为无论何时您访问字典项目，您都会得到一个可选的。

var response = Dictionary<String,Dictionary<String,Dictionary<String, Float>>>()

func valueForCurrency(currency :String, exchange :String) -> Float? {
    return response["current_rates"]?[exchange]?[currency]
}

解决方案 2. 在解析时将每个级别转换为字典。确保仍然检查可选值是否存在。

var response = Dictionary<String,Any>()

func valueForCurrency(currency :String, exchange :String) -> Float? {
    let exchanges = response["current_rates"] as? Dictionary<String,Any>

    let currencies = exchanges?[exchange] as? Dictionary<String,Any>

    return currencies?[currency] as? Float
}