问题

我有一个使用标准go Printf 函数签名的 Printer 接口：

type Printer interface {
    Printf(format string, tokens ...interface{})
}

我想使用 gomock 来模拟这个接口，但是我不确定如何正确设置 tokens ...interface{} 参数。

我原以为 Printf(gomock.Any(), gomock.Any()) 可以覆盖所有可能的情况（因为 tokens 编译为 []interface{}），但是似乎你需要为 N 个 token 设置一个明确的调用：

// 没有 token
mockPrinter.EXPECT().
    Printf(gomock.Any()).
    AnyTimes()

// 1 个 token
mockPrinter.EXPECT().
    Printf(gomock.Any(), gomock.Any()).
    AnyTimes()

// 2 个 token
mockPrinter.EXPECT().
    Printf(gomock.Any(), gomock.Any(), gomock.Any()).
    AnyTimes()

// ... 直到 N 个 token

有人知道有更好的方法吗？

<details>
<summary>英文:</summary>

I have a `Printer` interface that uses the standard go `Printf` function signature:

    type Printer interface {
        Printf(format string, tokens ...interface{})
    }

I would like to be able to mock this interface using [gomock](https://github.com/golang/mock), but I&#39;m not sure how setup the `tokens ...interface{}` argument properly. 

I expected that `Printf(gomock.Any(), gomock.Any())` would cover all potential cases (since `tokens` compiles to `[]interface{}`), but it appears you need to setup an explicit call for N number of tokens:

    // no tokens
    mockPrinter.EXPECT().
        Printf(gomock.Any()).
        AnyTimes()

    // 1 token
    mockPrinter.EXPECT().
        Printf(gomock.Any(), gomock.Any()).
        AnyTimes()

    // 2 tokens
    mockPrinter.EXPECT().
        Printf(gomock.Any(), gomock.Any(), gomock.Any()).
        AnyTimes()

    // ... up to N tokens

Does anyone know of a better way to do this?

</details>


# 答案1
**得分**: 2

当前版本的gomock不支持这个功能。也许你可以扩展它，并发送一个拉取请求。要理解为什么不可能，你需要查看为可变参数函数生成的模拟。

为了做到这一点，让我们看一下gomock存储库中的示例，特别是[./sample/mock_user/user.go][1]和[./sample/mock_user/mock_user.go][2]。

### 生成的模拟 ###

你会看到*Index*接口中有一个名为*Ellip*的函数，类似于你的*Printf*函数：

    type Index interface {
        // ...
        Ellip(fmt string, args ...interface{})
        // ...
    }

现在，这是*Ellip*的模拟函数的样子：

    func (_m *MockIndex) Ellip(_param0 string, _param1 ...interface{}) {
        _s := []interface{}{_param0}
        for _, _x := range _param1 {
            _s = append(_s, _x)
        }
        _m.ctrl.Call(_m, "Ellip", _s...)
    }

注意到什么奇怪的地方了吗？gomock创建了一个接口切片**_s**，用第一个参数进行初始化。然后它将可变参数追加到该接口切片**_s**中。

所以，明确一点，它不仅仅是将可变参数**_param1**追加到切片中。它通过迭代可变参数**_param1**，将每个单独的可变参数追加到新的切片中。

这意味着可变参数的切片并没有被保留下来。它被拆分了。

  [1]: https://github.com/rafrombrc/gomock/blob/9dcd4b2cd01be60f9fbabacce2a6ae1ed21ea48f/sample/user.go
  [2]: https://github.com/rafrombrc/gomock/blob/9dcd4b2cd01be60f9fbabacce2a6ae1ed21ea48f/sample/mock_user/mock_user.go

<details>
<summary>英文:</summary>

Not possible with the current version of gomock. Maybe you can extend it, and send a pull request in. To understand why it&#39;s not possible, you have to look at the mock generated for variadic functions.

To do that, let&#39;s look at the examples in gomock&#39;s repository, specifically [./sample/mock_user/user.go][1] and [./sample/mock_user/mock_user.go][2].

### Generated Mock ###
You&#39;ll see a function in the *Index* inteface called *Ellip*, which is like your *Printf* function:

    type Index interface {
        // ...
        Ellip(fmt string, args ...interface{})
        // ...
    }
Now, here&#39;s what the mocked function looks like for *Ellip*:

    func (_m *MockIndex) Ellip(_param0 string, _param1 ...interface{}) {
    	_s := []interface{}{_param0}
    	for _, _x := range _param1 {
    		_s = append(_s, _x)
    	}
    	_m.ctrl.Call(_m, &quot;Ellip&quot;, _s...)
    }
Notice anything odd? Well, gomock is creating a slice of interfaces, **_s**, initialized with the first parameter. Then it appends the variadic parameters to that slice of interfaces, **_s**.

So, to be clear, it doesn&#39;t just append the variadic parameter, **_param1**, to the slice. Each individual variadic from **_param1** is appended to the new slice, by iterating through it.

This means that the slice of variadic parameters is not preserved. It&#39;s broken out.


  [1]: https://github.com/rafrombrc/gomock/blob/9dcd4b2cd01be60f9fbabacce2a6ae1ed21ea48f/sample/user.go
  [2]: https://github.com/rafrombrc/gomock/blob/9dcd4b2cd01be60f9fbabacce2a6ae1ed21ea48f/sample/mock_user/mock_user.go

</details>



# 答案2
**得分**: 0

截至2017年10月1日，`gomock.Any()`对于可变参数的工作是正确的：https://github.com/golang/mock/pull/101

<details>
<summary>英文:</summary>

As of October 1, 2017, `gomock.Any()` works correctly for variadic args: https://github.com/golang/mock/pull/101

</details>