P.NAM.05 The getter family of methods used to access or retrieve data should not normally have the prefix get_

[Description]

Because of Rust's ownership semantics, both methods' parameters in following cases use shared reference &self or exclusive reference &mut self , which represent getter semantics.

getter semantics always mean to return an object but a reference in Rust's ownership conventions.

There are also some exceptions to use get_ prefix.

[Bad Case]


#![allow(unused)]
fn main() {
pub struct First;
pub struct Second;

pub struct S {
    first: First,
    second: Second,
}

impl S {
    // Bad: Shouldn't use 'get_' prefix to name accesssing member function.
    pub fn get_first(&self) -> &First {
        &self.first
    }

    // Bad：
    // `get_mut_first`, or `mut_first` are also not good.
    pub fn get_first_mut(&mut self) -> &mut First {
        &mut self.first
    }

    // set_ prefix is fine.
    pub fn set_first(&mut self, f: First) -> &mut First {
        self.first = f;
    }
}
}

[Good Case]


#![allow(unused)]
fn main() {
pub struct First;
pub struct Second;

pub struct S {
    first: First,
    second: Second,
}

impl S {
    // Ok
    pub fn first(&self) -> &First {
        &self.first
    }

    // Ok
    pub fn first_mut(&mut self) -> &mut First {
        &mut self.first
    }

    // set_ prefix is fine.
    pub fn set_first(&mut self, f: First) -> &mut First {
        self.first = f;
    }
}
}

[Exception]

However, there are also some exceptions: Only in cases to retrieve data by getter explicitly, could name with get_ prefix. For example, Cell::get could access the data in one Cell.

For getter checked in runtime, such as bounds checking, we could consider to add an Unsafe _unchecked methods. Generally, there would be following function signatures.


#![allow(unused)]
fn main() {
// Do some checks in runtime, such as bounds checking.
fn get(&self, index: K) -> Option<&V>;
fn get_mut(&mut self, index: K) -> Option<&mut V>;
// No runtime checking, use to improve performance in some case. 
// For example, when executed in an execution environment,which is impossible to trigger bounds checking.
unsafe fn get_unchecked(&self, index: K) -> &V;
unsafe fn get_unchecked_mut(&mut self, index: K) -> &mut V;
}

There is almost no such distinction between getter and type conversion (G.NAM.02). For instance, TemDir::path could be regarded as a getter, which represents the filesystem's path of temporary directory, and TemDir::into_path is in charge of sending converted data when deleting temporary directory to callee.

There would not result for redundancy with naming the method as path, because path itself is a getter, otherwise if you name it as get_path or as_path.

Implementations in StandardLibrary: