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https://github.com/rust-unofficial/patterns
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84 lines
2.6 KiB
Markdown
84 lines
2.6 KiB
Markdown
# Easy doc initialization
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## Description
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If a struct takes significant effort to initialize, when writing docs, it can be quicker to wrap your example with a
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function which takes the struct as an argument.
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## Motivation
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Sometimes there is a struct with multiple or complicated parameters and several methods.
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Each of these methods should have examples.
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For example:
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```rust,ignore
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struct Connection {
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name: String,
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stream: TcpStream,
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}
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impl Connection {
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/// Sends a request over the connection.
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///
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/// # Example
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/// ```no_run
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/// # // Boilerplate are required to get an example working.
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/// # let stream = TcpStream::connect("127.0.0.1:34254");
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/// # let connection = Connection { name: "foo".to_owned(), stream };
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/// # let request = Request::new("RequestId", RequestType::Get, "payload");
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/// let response = connection.send_request(request);
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/// assert!(response.is_ok());
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/// ```
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fn send_request(&self, request: Request) -> Result<Status, SendErr> {
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// ...
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}
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/// Oh no, all that boilerplate needs to be repeated here!
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fn check_status(&self) -> Status {
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// ...
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}
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}
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```
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## Example
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Instead of typing all of this boiler plate to create an `Connection` and `Request` it is easier to just create a wrapping dummy function which takes them as arguments:
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```rust,ignore
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struct Connection {
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name: String,
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stream: TcpStream,
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}
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impl Connection {
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/// Sends a request over the connection.
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///
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/// # Example
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/// ```
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/// # fn call_send(connection: Connection, request: Request) {
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/// let response = connection.send_request();
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/// assert!(response.is_ok());
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/// # }
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/// ```
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fn send_request(&self, request: Request) {
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// ...
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}
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}
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```
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**Note** in the above example the line `assert!(response.is_ok());` will not actually run while testing because it is inside of a function which is never invoked.
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## Advantages
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This is much more concise and avoids repetitive code in examples.
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## Disadvantages
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As example is in a function, the code will not be tested. (Though it still will checked to make sure it compiles when running a `cargo test`)
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So this pattern is most useful when need `no_run`. With this, you do not need to add `no_run`.
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## Discussion
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If assertions are not required this pattern works well.
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If they are, an alternative can be to create a public method to create a dummy instance which is annotated with `#[doc(hidden)]` (so that users won't see it).
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Then this method can be called inside of rustdoc because it is part of the crate's public API.
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