ios - CoreData 如何将数据发送到另一个 View Controller

Question

我正在尝试在 IOS 中实现功能，其中用户单击 UIPickerController 即 didSelectRow 并将数据发送到另一个 View Controller

我使用的是 IOS 10，这里的 CoreData 展示了我是如何做到这一点的。

// fetch data from the Core data model
   func fetchData(){
    // fetch the entity
    //1st stage:what is going to fetchgo and  fetch ProductDetails
    let fetchRequest : NSFetchRequest<ProductDetails>
         = ProductDetails.fetchRequest()
     // perform the above action :
    do {

          self.data = try context.fetch(fetchRequest)

        for d in data {

            coursetitle = d.courseName!
            print("course title is: \(coursetitle)")

        }


          self.PickerCourse.reloadAllComponents()

    }
    catch {
        // handle any errors

        let error = error as NSError
        print("A Error has occurred while fetching data: \(error) !")

    }// end of catch statement


}// end of fetch data method

上面是我的获取数据方法，它从 Core Data 获取数据

然后我通过我的加载方法将其加载到 UIPicker

//将数据加载到选择器

func loadProductData(){

    if let item = productsToEdit {
        // can invoke relational ie toProductDetails
        if let store = item.toStore{

            var index = 0
            repeat{
                // populate in UIPicker 
                let sIndex = data[index]
                if sIndex.courseName == store.name
                {
                    PickerCourse.selectRow(index, 
                    inComponent: 0, animated: false)
                    break // out of the loop
                }
                index += 1 // increment index by 1

            }while (index < data.count)
        }

    }// end of item check

}// end of load product data

问题就在这里

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, 

  inComponent component: Int) {


    if component == 0{

        // what ever the row is selected assign the value to variable.
        CourseSelectedIndex = row
       productData = [data[row]]
        print("user has selected row at: \(productData)")
        //even if I include a segue here I get a error state Array can
        // not be assign to NSObject


    }


}

我希望以上提供的信息足够多，非常感谢您在正确方向上的支持。

谢谢

Answer 1

大家好，我解决了我的问题

在创建新信息示例实体名称表属性名称时，根据我对“核心数据”的理解，不确定技术术语是什么

名字=猫

名称将有其 ID，该 ID 称为 objectId。您可以使用 objectId 通过字符串匹配和其他技术来获取数据。但是，如果您想使用旧时尚方法使用数组索引值将信息传递到多个表单

那么这应该可以解决你的问题

首先从核心数据中获取数据并将其加载到数组中

var ArrayName: [String] = []

func fetchData(){

    print("you are outside the do loop fetch 
        method for debug purpose only ")

    do {

        data = try context.fetch(ProductDetails.fetchRequest())
        print("you are inside the do ...")

        for each in data {

            print("Course Name :  \(each.courseName!) 
             \n Price : \(each.price)\n \n Description: 
               \(each.desription) \n")


            ArrayName.append( each.Name!)// append to a array 
            print("You are in the Fetch method ...")

        }// end of for each


    }
    catch {
        // handle any errors


        print("What a nob you are indeed !")



    }// end of catch statement


}// end of fetch data method

当然，您需要将数组存储在全局某个地方，以便您可以从任何 View Controller 访问它

现在您需要将数据加载到 UIPicker Controller

//将数据加载到选择器中//为核心数据创建一个NS对象 var productsToEdit:产品详细信息？ 函数 loadProductData(){

    if let item = productsToEdit {
        // can invoke relational ie toProductDetails
        if let store = item.toStore{

            var index = 0
            repeat{

                let sIndex = data[index]
                if sIndex.Name == store.name
                {
                    PickerCourse.selectRow(index, 
                     inComponent: 0, animated: false)
                    break // out of the loop
                }
                index += 1 // increment index by 1

            }while (index < data.count)
        }

    }// end of item check

}// end of load product data

确保您在 View 控件中按以下顺序运行这些加载方法

加载数据()获取数据()

还在你的 UIPicker Controller 中确保你有以下内容

func pickerView(_ pickerView: UIPickerView, titleForRow 
row: Int,  forComponent component: Int) -> String? {


    return ArrayName[row]

}

func pickerView(_ pickerView: UIPickerView, 
numberOfRowsInComponent component: Int) -> Int {
    // return number of rows within UIPickerView
    return data.count  
}

func numberOfComponents(in pickerView: UIPickerView) -> Int {
    // return the number of  ' Colums to display

    return 1 
}



func pickerView(_ pickerView: UIPickerView, 
 didSelectRow row: Int, inComponent component: Int) {

    if component == 0{

        // what ever the row 
        is selected assign the value to variable.
        CourseSelectedIndex = row

        print("user has selected row at: \(productData)")

    }


}

func pickerView(_ pickerView: UIPickerView, 
 didSelectRowAtIndexPath indexPath: NSIndexPath) {



 }

请记住，此代码的大部分内容都是从我的原始代码中编辑的，其中某些变量可能会显示为未声明等...

如果您发现这有用，请给予信任。如果我错了，同样纠正我。我们来这里是为了学习。

谢谢