英文:
Type annotations needed for none variant - ergonomics
问题
我有一个结构体，其中有一个名为 'payload' 的字段，其类型为 Option<T>，其中 T 可以是多种原始整数类型之一。像这样：
pub struct Request<T: MyIntTrait> {
pub cmd: Cmd,
pub payload: Option<T>,
其他一些字段...
}
当使用 None 实例化此结构体时，显然需要类型注释：
let req: Request<u8> = Request { cmd: Cmd::Get, payload: None, ...}
或者像这样：
let req = Request { cmd: Cmd::Get, payload: None::<u8>, ...}
这使得 API 不够人性化，使用起来很反直觉。有人有什么办法可以解决这个问题，还是我只能忍受它？
英文:
I have a struct with a field 'payload' of Option<T> where T can be one of several primitive integer types. Like so:
pub struct Request<T: MyIntTrait> {
pub cmd: Cmd,
pub payload: Option<T>,
a bunch of other fields...
}
When instantiating this struct with None as its payload obviously type annotations are needed:
let req: Request<u8> = Request { cmd: Cmd::Get, payload: None, ...}
or like this:
let req = Request { cmd: Cmd::Get, payload: None::<u8>, ...}
This makes for a very unergonomic api that is counterintuitive to use.
Has anybody got an idea how to get around this or will I just have to live with it?
答案1
得分: 1
除非T可以在其他地方被推断出来，否则你必须以某种方式指定它。在你的情况下，你可以为类型参数指定一个默认值，这可能足够了：
pub struct Request<T: MyIntTrait = u8>
英文:
Unless the T can be inferred somewhere else, you have to specify it somehow. You could specify a default for the type argument, which may be sufficient in your case:
pub struct Request<T: MyIntTrait = u8>
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