ios - 第一次单击按钮时未显示数据

Question

我的应用程序正在解码来自 PHP 网络服务的一些 JSON 数据，但是当我第一次点击获取按钮时，数据没有显示在标签上。

在调试中，我可以看到数据已传递到数组，但未传递到 View Controller 中的标签。

你能帮我解决这个问题吗？

提前致谢

阿德尔莫

点击按钮

@IBAction func btn_ler(_ sender: Any)
    {

        //txt_matricula.text = ""
        //txt_marca.text = ""
        //txt_modelo.text = ""

        obter_dados_veiculo(matricula: input_matricula.text!)

        for veiculo in a_veiculos
        {
            txt_matricula.text = veiculo.MATRICULA
            txt_modelo.text = veiculo.MODELO
            txt_marca.text = veiculo.MARCA
        }

        //lbl_num_servicos.text = String( a_veiculos.count)
    }

获取JSON的函数

func obter_dados_veiculo (matricula : String)
    {
        //Variável que vai conter o URL
        let v_url = "http://arshome.hopto.org/Domingues/DEV/api_get_veiculos.php?MATRICULA=" + matricula

        let o_url = URL(string: v_url)

        URLSession.shared.dataTask(with: o_url!)
        {
            (data, response, error) in

            do
            {
                let matriculas = try JSONDecoder().decode([s_veiculo].self, from: data!)


                //for matricula in matriculas
                //{
                    //print(matricula.MATRICULA)
                a_veiculos = []
                    a_veiculos.append(contentsOf: matriculas)
                //}
            }
            catch
            {
                print("We have an error!")
                //self.txt_matricula.text = "We have an error!"
            }
            print( a_veiculos.count)
            }.resume()
    }

Answer 1

你必须在你的obter_dados_veiculo方法中添加一个完成闭包，如下所示:

func obter_dados_veiculo (matricula : String, completion:@escaping(Bool,Error?)->())
{
    //Variável que vai conter o URL
    let v_url = "http://arshome.hopto.org/Domingues/DEV/api_get_veiculos.php?MATRICULA=" + matricula

    let o_url = URL(string: v_url)

    URLSession.shared.dataTask(with: o_url!)
    {
        (data, response, error) in

        do
        {
            let matriculas = try JSONDecoder().decode([s_veiculo].self, from: data!)


            //for matricula in matriculas
            //{
            //print(matricula.MATRICULA)
            a_veiculos = []
            a_veiculos.append(contentsOf: matriculas)
            completion(true,nil)
            //}
        }
        catch let error as NSError
        {
            print("We have an error!")
            completion(false,error)
            //self.txt_matricula.text = "We have an error!"
        }
        print( a_veiculos.count)
        }.resume()
}

然后像下面这样调用它:

@IBAction func btn_ler(_ sender: Any)
{

    //txt_matricula.text = ""
    //txt_marca.text = ""
    //txt_modelo.text = ""

    obter_dados_veiculo(matricula: input_matricula.text!) { (success, error) in
        for veiculo in self.a_veiculos
        {
            txt_matricula.text = veiculo.MATRICULA
            txt_modelo.text = veiculo.MODELO
            txt_marca.text = veiculo.MARCA
        }
    }

    //lbl_num_servicos.text = String( a_veiculos.count)
}