Swift中的變數未傳入POST引數

我正在嘗試使用 POSTMAN Api 按國家/地區獲取城市。當我沒有將任何變數帶入引數時，請求按預期作業。但是，當我嘗試使用全域變數作為引數時，它回傳空。如果它被編碼為這樣，它作業得很好：“國家”：“尼日利亞”（其他一切都一樣）

下面的代碼：

let myCountry = selectedCountryString.lowercased().trimmingCharacters(in: .whitespacesAndNewlines)
    guard let url = URL(string: "https://countriesnow.space/api/v0.1/countries/population/cities/filter") else {
        return
    }
    
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")   
    let body: [String: Any] = [
    
        "limit": 10,
        "order": "dsc",
        "orderBy": "value",
        "country": "\(myCountry)"

    ]
    
    request.httpBody = try? JSONSerialization.data(withJSONObject: body, options: .fragmentsAllowed)
    let task = URLSession.shared.dataTask(with: request) {data, _, error in
        guard let data = data, error == nil else {
            return
        }
        do{                
            let response = try JSONDecoder().decode(CitiesPopModel.self, from: data)
            onCompletion(response)
        } 
        catch {
            print("Error country -> \(myCountry)")              
        }
    }       
    task.resume()       
}

我將我的代碼切換到這個，它現在正在使用變數：

func callCitiesByPopAPI(completion: @escaping (CitiesPopModel?, Error?) -> ()) {
     let url = "https://countriesnow.space/api/v0.1/countries/population/cities/filter"
     
     let parameters: [String: Any] = [
        "limit": 20,
        "order": "dsc",
        "orderBy": "value",
        "country": selectedCountryString
     ]
     
     AF.request(url, method: .post, parameters: parameters, encoding: JSONEncoding.default).responseDecodable(of: CitiesPopModel.self) { response in
         if let error = response.error {
             completion(nil, error)
             return
         }
         if let result = response.value {
             completion(result, nil)
             print("City pop model result is \(result)")
             return
         }
     }
 }

uj5u.com熱心網友回復：

不用擔心，您必須像這樣傳遞 selectedCountryString 值，然后一切順利

讓 selectedCountryString = "印度"

uj5u.com熱心網友回復：

為此替換 HttpHeaderField 的值：

request.setValue("application/json", forHTTPHeaderField: "Accept")
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")

并為此替換 httpBody：

request.httpBody = body.percentEncoded()

我在阿爾及利亞進行了測驗，它有效。

extension Dictionary {
    func percentEncoded() -> Data? {
        map { key, value in
            let escapedKey = "\(key)".addingPercentEncoding(withAllowedCharacters: .urlQueryValueAllowed) ?? ""
            let escapedValue = "\(value)".addingPercentEncoding(withAllowedCharacters: .urlQueryValueAllowed) ?? ""
            return escapedKey   "="   escapedValue
        }
        .joined(separator: "&")
        .data(using: .utf8)
    }
}

extension CharacterSet {
    static let urlQueryValueAllowed: CharacterSet = {
        let generalDelimitersToEncode = ":#[]@" // does not include "?" or "/" due to RFC 3986 - Section 3.4
        let subDelimitersToEncode = "!$&'()* ,;="
        
        var allowed: CharacterSet = .urlQueryAllowed
        allowed.remove(charactersIn: "\(generalDelimitersToEncode)\(subDelimitersToEncode)")
        return allowed
    }()
}

uj5u.com熱心網友回復：

這是我的測驗代碼，展示了如何從服務器獲取資料，使用變數作為POST請求的引數（國家），并將其顯示在視圖中。對我來說效果很好。

struct ContentView: View {
    @State var cityPop = CitiesPopModel()
    
    var body: some View {
        List(cityPop.data) { data in
            VStack {
                Text(data.city).foregroundColor(.blue)
                ScrollView(.horizontal) {
                    HStack {
                        ForEach(data.populationCounts) { pop in
                            VStack {
                                Text(pop.year)
                                Text(pop.sex)
                                Text(pop.value).foregroundColor(.blue)
                            }
                        }
                    }
                }
            }
        }
        .onAppear {
            getCountry(country: "Australia") { result in
                if let popData = result {
                    cityPop = popData
                }
            }
        }
    }
    
    func getCountry(country: String, completion: @escaping(CitiesPopModel?) -> Void) {
        
        guard let url = URL(string: "https://countriesnow.space/api/v0.1/countries/population/cities/filter") else {
            return
        }
        
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        let body: [String: Any] = [
            "limit": 10,
            "order": "dsc",
            "orderBy": "value",
            "country": country
        ]
        request.httpBody = try? JSONSerialization.data(withJSONObject: body, options: .fragmentsAllowed)
        
        URLSession.shared.dataTask(with: request) { data, _, error in
            guard let data = data, error == nil else { return }
            do {
                let response = try JSONDecoder().decode(CitiesPopModel.self, from: data)
                return completion(response)
            }
            catch {
                print("Error country -> \(country)")
            }
            completion(nil)
        }.resume()
    }
}


// MARK: - CitiesPopModel
struct CitiesPopModel: Codable {
    var error: Bool = false
    var msg: String = ""
    var data: [City] = []
}

// MARK: - City
struct City: Identifiable, Codable {
    let id = UUID()
    let city: String
    let country: String
    let populationCounts: [Population]
    
    enum CodingKeys: String, CodingKey {
        case city, country, populationCounts
    }
}

// MARK: - Population
struct Population: Identifiable, Codable {
    let id = UUID()
    let year, value, sex, reliabilty: String
    
    enum CodingKeys: String, CodingKey {
        case year, value, sex, reliabilty
    }
}

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