Core Data自定义策略的选择器语法是什么? [英] What is the selector syntax for Core Data custom policies?

问题描述

我正在尝试使用Core Data实现非常基本的自定义迁移.最初创建的单个属性为Integer 16，其值为0或1.在新的模型版本中，此属性更改为Boolean，并且下面的迁移策略应对此进行处理.我已经看到了几个用Swift编写的示例，它们似乎并没有使可访问性打开/公开，也没有添加@objc使其可被Objective-C访问.我这样做是为了消除它无法正常工作的任何原因.

I am trying to implement a very basic custom migration with Core Data. A single property was initially created as an Integer 16 with values of 0 or 1. In the new model version this property is changed to Boolean and the migration policy below should handle it. I have seen several examples written in Swift and they don't appear to make the accessibility open/public or add @objc to make it accessible to Objective-C. I have done this to eliminate any reason it not working.

我已使用以下表达式为用于实体映射的自定义策略创建了映射模型.

I've created the mapping model with the custom policy for the entity mapping with the following expression.

FUNCTION($entityPolicy, "convertInteger:" , $source.active)

由于无法识别选择器而一直失败.具体来说，它会收到以下错误.

It keeps failing because the selector is not recognized. Specifically it gets the following error.

unrecognized selector sent to instance

我尝试了很多变化.

• convertInteger:
• 转换(整数:)
• convertInteger(_:)

我无法进行任何改动.此表达式的有效选择器是什么?

I am unable to get any variation to work. What is a valid selector for this expression?

在Swift代码中，我在初始化器中放置了一个断言，该断言通过了，但是我不能在策略的表达式中使用相同的选择器.

In the Swift code I put an assertion in the initializer and it passes, but I cannot use that same selector in the expression for the policy.

import CoreData

@objc
open class IntegerToBooleanMigrationPolicy: NSEntityMigrationPolicy {

    @objc
    public override init() {
        super.init()
        assert(responds(to: #selector(convert(integer:))), "Policy does not respond to selector!")
    }

    @objc
    open func convert(integer: Int16) -> Bool {
        debugPrint("Converting \(integer) to boolean")
        return integer == 1
    }

}

推荐答案

将代码段粘贴到Swift REPL之后，我评估了以下表达式:

After pasting your code snippet into the Swift REPL, I evaluated the following expression:

20> #selector(IntegerToBooleanMigrationPolicy.convert(integer:))
$R1: Selector = "convertWithInteger:"

这表明convertWithInteger:是您应在映射表达式中使用的选择器.

That suggests convertWithInteger: is the selector you should use in the mapping expression.

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