类型只能包含一个@Inject构造函数 [英] Types may only contain one @Inject constructor

问题描述

data class AuthDataModel @Inject constructor(
                   var username: String = "",
                   var password: String = "",
                   var mobileData: String = "

说明

我正在尝试将身份验证数据模型注入kotlin中的身份验证视图模型，但是它不能与message一起编译(类型只能包含一个@Inject构造函数)

Explanation

I am trying to inject authentication data model to authentication view model in kotlin, but it does not compile with message("Types may only contain one @Inject constructor)

推荐答案

将我的评论移至答案:

如果您具有带有默认参数的构造函数，那么Kotlin实际上会生成其他构造函数.在您的情况下，您有3个arg构造函数，其中所有都是可选的，总共生成4个构造函数. Kotlin显然还将主构造函数上的所有注释也与所有生成的注释相关联，这意味着您最终得到了4个@Inject构造函数.

If you have a constructor with default arguments, Kotlin actually generates additional constructors. In your case, you have a 3 arg constructor where all are optional, which generates a total of 4 constructors. Kotlin apparently associates any annotations on the primary constructor with all the generated ones as well, which means you ended up with 4 @Inject constructors.

您有两个选择:

第一个，正如您自己提到的，删除所有默认值.如果没有默认值，则仅使用注释生成一个构造函数.

The first, as you mentioned yourself, remove all the default values. If there are no default values, only one constructor is generated with the annotation.

或者，您也可以自己创建其他构造函数并将其指向主构造函数.这也可以让您手动指定仅一个具有@Inject注释，而其他人则没有.基本上:

Alternatively, you can also create additional constructors yourself and point it to the primary. This would also let you manually specify only one to have the @Inject annotation, while the others don't. Basically:

data class AuthDataModel @Inject constructor(
                   var username: String,
                   var password: String,
                   var mobileData: String) {
    constructor(username: String) : this(username, "", "") {}
    constructor(username: String, password: String) : this(username, password, "") {}
}

不使用默认值会阻止生成多个@Inject构造函数，并且辅助构造函数应该 ¹ 保持所有功能正常运行.这基本上是在重载构造函数，并且当某些变量是可选的时，这等效于您在Java中所做的事情.因此应该没问题.

Not using default values prevents multiple @Inject constructors from being generated, and the secondary constructors should¹ keep everything functioning as expected. This is basically overloading the constructor, and it's equivalent to what you'd do in Java when certain variables are optional. Should therefore be fine.

^{1:我已经有一段时间没有使用Android了，而且我从未使用过@Inject.如果选项2不起作用(如@Inject不允许，或不能按预期方式工作，等等)，则仅保留选项1，并要求显式传递每个参数.但是，调用主构造函数的辅助构造函数应该足以保持一切正常.}

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