https://github.com/dtolnay/readonly

Struct fields that are made read-only accessible to other modules
https://github.com/dtolnay/readonly

Last synced: 10 days ago
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Struct fields that are made read-only accessible to other modules

• Host: GitHub
• URL: https://github.com/dtolnay/readonly
• Owner: dtolnay
• License: apache-2.0
• Created: 2019-03-27T02:23:16.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2024-03-26T05:26:29.000Z (8 months ago)
• Last Synced: 2024-05-09T09:38:18.587Z (6 months ago)
• Language: Rust
• Homepage:
• Size: 160 KB
• Stars: 206
• Watchers: 3
• Forks: 11
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Funding: .github/FUNDING.yml
  • License: LICENSE-APACHE

Awesome Lists containing this project

README

        
Readonly

========

[](https://github.com/dtolnay/readonly)

[](https://crates.io/crates/readonly)

[](https://docs.rs/readonly)

[](https://github.com/dtolnay/readonly/actions?query=branch%3Amaster)

This crate provides an attribute macro to expose struct fields that are readable

and writable from within the same module but readable only outside the module.

```toml

[dependencies]

readonly = "0.2"

```

## Syntax

Place `#[readonly::make]` on a braced struct or tuple struct. This will make all

fields of the struct publicly readable according to their individual visibility

specifiers, but not writable from other modules.

```rust

mod m {

    #[readonly::make]

    pub struct S {

        pub n: i32,

    }

    impl S {

        pub fn demo(&mut self) {

            // Can read and write from inside the same module.

            println!("{}", self.n);

            self.n += 1;

        }

    }

}

fn demo(s: &mut m::S) {

    // From outside the module, can only read.

    println!("{}", s.n);

    // Does not compile:

    //s.n += 1;

}

```

The error appears as follows.

```console

error[E0594]: cannot assign to data in a dereference of `m::S`

  --> readme.rs:21:5

   |

21 |     s.n += 1;

   |     ^^^^^^^^ cannot assign

```

Optionally, place `#[readonly]` on individual struct fields to make just those

fields publicly readable, without affecting other fields of the struct.

```rust

#[readonly::make]

pub struct S {

    // This field can be read (but not written) by super.

    #[readonly]

    pub(super) readable: i32,

    // This field can be neither read nor written by other modules.

    private: i32,

}

```




#### License



Licensed under either of Apache License, Version

2.0 or MIT license at your option.








Unless you explicitly state otherwise, any contribution intentionally submitted

for inclusion in this crate by you, as defined in the Apache-2.0 license, shall

be dual licensed as above, without any additional terms or conditions.