尝试访问词典时出现Swift错误:`找不到成员'下标'

Question

这不会编译: 我尝试过几种不同的东西; 声明Dictionary的不同方法,更改其类型以匹配数据的嵌套.我也试着明确说我Any是一个集合所以它可以下标.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

我们来看看吧

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,因为无论何时访问字典项,您都会获得可选项.

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Dictionary.确保仍然检查是否存在可选值.

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
}