iOS 8 Swift - 保存多个实体的数据 [英] iOS 8 Swift - saving data of multiple entities

问题描述

我的练习应用程式有以下实体关系。

I have the following entity relationship for my practice app.

我困在一个由多个实体组成的新配方的保存部分。

And I'm stuck with the saving part of a new recipe that consists of multiple entities.

我有RecipeIngredient中间（联合）实体的原因是我需要一个额外的属性，将通过食谱存储不同量的成分。

The reason I have RecipeIngredient intermediate(joint) entity is that I need an additional attribute that will store a varying amount of an ingredient by recipe.

这里是实现，显然缺少金额值分配每个新的成分，因为我不确定是否需要初始化这个RecipeIngredient实体，或者即使我这样做，我不知道如何粘合他们所有为一个食谱。

Here is the implementation which is obviously missing the assignment of the amount value to each new ingredient as I was not certain about the need for initialising this RecipeIngredient entity or even if I did, I wouldn't know how to glue them all up as one recipe.

@IBAction func saveTapped(sender: UIBarButtonItem) {

    // Reference to our app delegate
    let appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate

    // Reference moc
    let context: NSManagedObjectContext = appDel.managedObjectContext!
    let recipe = NSEntityDescription.entityForName("Recipe", inManagedObjectContext: context)
    let ingredient = NSEntityDescription.entityForName("Ingredient", inManagedObjectContext: context)


    // Create instance of data model and initialise
    var newRecipe = Recipe(entity: recipe!, insertIntoManagedObjectContext: context)
    var newIngredient = Ingredient(entity: ingredient!, insertIntoManagedObjectContext: context)

    // Map properties
    newRecipe.title = textFieldTitle.text
    newIngredient.name = textViewIngredient.text

    ...

    // Save Form
    context.save(nil)

    // Navigate back to root vc
    self.navigationController?.popToRootViewControllerAnimated(true)

}

推荐答案

需要初始化这个RecipeIngredient实体，或者即使我做了，我也不知道如何将它们全部粘合成一个配方。

I was not certain about the need for initialising this RecipeIngredient entity or even if I did, I wouldn't know how to glue them all up as one recipe.

您将需要创建RecipeIngredient实例，就像对任何其他实体一样。你可以做基本上相同的事情，你曾经做过。

You'll need to create the RecipeIngredient instance(s) just as you would for any other entity. You can do essentially the same thing that you've done e.g. for Recipe:

// instantiate RecipeIngredient
let recipeIngredient = NSEntityDescription.entityForName("RecipeIngredient", inManagedObjectContext: context)
let newRecipeIngredient = RecipeIngredient(entity:recipeIngredient!, insertIntoManagedObjectContext:context)
// set attributes
newRecipeIngredient.amount = 100
// set relationships
newRecipeIngredient.ingredient = newIngredient;
newRecipeIngredient.recipe = newRecipe;

请注意，由于您提供了成分和 recipe ，您不需要也将 newRecipeIngredient 添加到 newRecipe。或或添加 newRecipeIngredient 到 newIngredient.recipes 。

Note that since you've provided inverse relationships for ingredient and recipe, you don't need to also add newRecipeIngredient to newRecipe.ingredients or add newRecipeIngredient to newIngredient.recipes.

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