英文:
why is a simple struct field type not supported in GAE datastore?
问题
我的单元测试在报错，错误信息如下：
>&errors.errorString{s:"datastore: unsupported struct field type: sus.Version"}
我有一个测试结构体类型，我试图将其保存到 GAE 数据库中：
type foo struct{
sus.Version
}
其中 sus.Version 是一个接口：
type Version interface{
GetVersion() int
getVersion() int
incrementVersion()
decrementVersion()
}
我尝试使用两种不同的 Version 实现来运行我的测试，首先是将其作为 int 的别名：
type version int
其次是将其作为一个结构体：
type version struct{
val int
}
在 Version 接口的方法中，接收者类型为 (v *version)，这样做是为了确保 decrement 和 increment 方法能够更新调用它们的版本，而不仅仅是复制一个副本。我不确定为什么这样做不起作用，可能是因为它是一个匿名字段？或者可能是因为它是一个指向 int 或结构体的指针，而不是实际的 int 或结构体？
英文:
my unit test is failing with message:
>&errors.errorString{s:"datastore: unsupported struct field type: sus.Version"}
I have a test struct type that I am trying to save to GAE datastore:
type foo struct{
sus.Version
}
where sus.Version is the interface:
type Version interface{
GetVersion() int
getVersion() int
incrementVersion()
decrementVersion()
}
I have tried running my test with two Version implementations, first where it is just an alias for an int:
type version int
and secondly as a struct:
type version struct{
val int
}
where the Version interface methods are given receiver type (v *version), it needs to be a pointer so decrement and increment actually update the version they are called on and not just a copy. I'm not sure why this isn't working, potentially because it's an anonymous field? or perhaps because it's a pointer to an int or struct rather than an actual int or struct?
答案1
得分: 6
datastore包不允许使用所有类型。特别是，它只允许使用以下类型：
- 有符号整数（int、int8、int16、int32和int64）
- 布尔值
- 字符串
- float32和float64
- []byte（长度最多为1兆字节）
- 任何底层类型为上述预声明类型之一的类型
- ByteString
- *Key
- time.Time（以微秒精度存储）
- appengine.BlobKey
- appengine.GeoPoint
- 所有字段都是有效值类型的结构体
- 上述任何类型的切片
请注意，这不包括"任何接口类型"。
英文:
The datastore package doesn't allow all types to be used. In particular, it only allows the following types to be used:
<pre>
- signed integers (int, int8, int16, int32 and int64),
- bool,
- string,
- float32 and float64,
- []byte (up to 1 megabyte in length),
- any type whose underlying type is one of the above predeclared types,
- ByteString,
- *Key,
- time.Time (stored with microsecond precision),
- appengine.BlobKey,
- appengine.GeoPoint,
- structs whose fields are all valid value types,
- slices of any of the above.
</pre>
Note that this doesn't include "any interface type".
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