go - 无法创建模拟 Google Cloud Storage 的接口(interface)

Question

我正在尝试创建一个接口(interface)来抽象谷歌云存储。

我有以下接口(interface):

type Client interface {
    Bucket(name string) *BucketHandle
    Close() error
}

type BucketHandle interface {
    Create(context.Context, string, *storage.BucketAttrs) error
    Delete(context.Context) error
    Attrs(context.Context) (*storage.BucketAttrs, error)
}

还有我的代码

type Bucket struct {
    handler Client
}

func NewStorage(ctx context.Context, bucketName string) Bucket {
    var bkt Bucket
    client, err := storage.NewClient(ctx)
    if err != nil {
        return Bucket{}
    }

    bkt.handler = client
    return bkt
}

我收到以下错误: cannot use client (variable of type *storage.Client) as Client value in assignment: wrong type for method Bucket
goland 显示以下内容

Cannot use 'client' (type *Client) as type Client Type does not implement 'Client' need method: Bucket(name string) *BucketHandle have method: Bucket(name string) *BucketHandle 

我不知道为什么类型不一样。

Answer 1

Cannot use 'client' (type *Client) as type Client Type does not implement 'Client' need method: Bucket(name string) *BucketHandle have method: Bucket(name string) *BucketHandle

这个错误没有任何问题。它看起来具有误导性的原因是因为您创建了一个与库中的具体结构同名的接口(interface)，即 BucketHandle
密切注意两个函数中返回类型之间的区别:

// In your interface, the return type is an interface that you created
Bucket(name string) *BucketHandle

// In the library, the return type is a concrete struct that exists in that lib
Bucket(name string) *BucketHandle

您需要修改 Client接口(interface)到以下，它应该可以正常工作。

type Client interface {
    Bucket(name string) *storage.BucketHandle
    Close() error
}