Crate datastruct 

DataStruct.rs

The library provides a derive macro to automatically implement “plain methods” for data structures.

Currently Available:

• Default: Standard Default, lib-specific DataStruct::data_default and constant default ConstDataStruct::DEFAULT.
• Debug: Manual Debug filter.
• Comparison: Standard Eq, PartialEq, Ord, PartialOrd.
• Operations: Standard Add(Assign), Sub(Assign), Mul(Assign), Div(Assign).

Unlike standard derive macros, the DataStruct macro accepts user-defined behaviors without writing implementation code.

Basic Syntax

To configure the meta options of the generator, add #[dstruct(options)] before your definition.

To configure the fields’ options, add #[dfield(options)] before your field declaration.

use datastruct_derive::DataStruct;

#[derive(DataStruct)]
#[dstruct()]
struct Data {
    #[dfield()]
    field: u32,
}

You can define the meta attributes multiple times, and the last declaration of each attribute will be used to generate the code.

For example,

#[dfield(no_debug, cmp(eq = false))]
#[dfield(cmp(eq = true))]

is equivalent to

#[dfield(no_debug, cmp(eq = true))]

Api Document

Default

Default Implementation

All default implementations are like:

struct NeedDefault {
    field1: usize,
    field2: String,
}

// generated code
let default: NeedDefault = {
    let field1: usize = 42;
    let field2: String = "Something default".to_string();
    NeedDefault {
        field1,
        field2,
    }
};

That means you can refer to other fields when initializing the default value.

use datastruct::DataStruct;

#[derive(DataStruct)]
#[dstruct(default)]
struct MyDefault {
    #[dfield(default = "second + first")]
    manual: usize,
    #[dfield(default = "40", seq = -1)]
    second: usize,
    #[dfield(default = "2", seq = -2)]
    first: usize,
}

// generated code
impl ::datastruct::DataStruct for MyDefault {
    fn data_default() -> Self {
        let first: usize = 2;
        let second: usize = 40;
        let manual: usize = second + first;
        Self {
            first,
            second,
            manual,
        }
    }
}

default

Ask the macro to generate an implementation of datastruct::DataStruct, which offers a runtime-default value but does not pollute the namespace.

Syntax:

• #[dstruct(default)]

Restriction:

• All fields must be provided with default value.

Field Configuration:

• #[dfield(default = xxx)]

  The literal expression should be wrapped inside a string, like this:

  
  #[dfield(default = "field + another")]
  #[dfield(default = "42_usize")]

  If no default value is provided, the field will be considered uninitialized and default-related code cannot be generated.

• #[dfield(seq = xxx)] | #[dfield(sequence = xxx)] where xxx is isize

  Change the sequence of the fields. By default, the sequence to initialize the fields is the same as how they are declared. The sequence option can help reorganize the process. Fields that are not tagged with seq = isize will inherit from the default sequence. You can also set the index with negative numbers.

  
  #[dstruct(default)]
  struct Data {
      field: u8,  // seq = 0
      #[dfield(seq = -1)]
      before: u8, // default seq = 1, seq = -1
  }

const

Ask the macro to generate an implementation of datastruct::ConstDataStruct, which offers a compile-time const default value but does not pollute the namespace.

Syntax:

• #[dstruct(const)]

Restriction:

• All fields must be provided with const default value.

Field Configuration:

• Inherits from default.

std_default

The same as default, but implement std::default::Default instead.

Syntax:

• #[dstruct(std_default)]

Restriction:

• All fields must be provided with default value.

Field Configuration:

• Inherits from default.

Warning:

• This may pollute the namespace, and IDE may not be able to identify the implementation.

partial

Partially default implementation.

This will produce something like:

use datastruct::DataStruct;

#[derive(DataStruct)]
#[dstruct(partial)]
struct Data {
    #[dfield(default = "10")]
    value1: u32,
    value2: u32,
}

// generated code
impl Data {
    pub fn partial_default(value2: u32) -> Self {
        Self {
            value1: 10,
            value2,
        }
    }
}

Syntax:

• #[dstruct(partial)]

Field Configuration:

• Inherits from default.

Setter and Getter

set

Generate default setter for fields.

Setter Type:

• full | all: Both set and with. (Default.)
• set: set_field_name(&mut self, value). Set the structure’s value.
• with: with_field_name(self, value) -> Self. Internally set the structure’s value and return itself.
• no: Ignore the field.

Syntax:

• #[dstruct(set)]: Default setter configuration.
• #[dstruct(set = "setter_type")]: Set default setter configuration to setter_type.

Field Configuration:

• #[dfield(set)]: Inherit the setter configuration from the structure. Typically, you don’t need to specify this.
• #[dfield(set = "setter_type")]: Override the default setter configuration.

Example:

use datastruct::DataStruct;

#[derive(DataStruct)]
#[dstruct(set)] // equivalent to `set = "full"`
struct Data {
    auto_set: usize,
    #[dfield(set = "no")]
    no_set: usize,
    #[dfield(set = "set")]
    only_set: usize,
}

// generated code
impl Data {
    pub fn set_auto_set(&mut self, auto_set: usize) {
        self.auto_set = auto_set;
    }
    pub fn set_only_set(&mut self, only_set: usize) {
        self.only_set = only_set;
    }

    pub fn with_auto_set(mut self, auto_set: usize) -> Self {
        self.auto_set = auto_set;
        self
    }
}

get

Generate default getter for fields.

Setter Type:

• full | all: Both move and get.
• get: field_name(&self) -> &value. Get the structure’s field’s reference. (Default.)
• move: get_field_name(self) -> move. Move the field out of the structure.
• no: Ignore the field.

Syntax:

• #[dstruct(get)]: Default getter configuration.
• #[dstruct(get = "getter_type")]: Set default getter configuration to getter_type.

Field Configuration:

• #[dfield(get)]: Inherit the getter configuration from the structure. Typically, you don’t need to specify this.
• #[dfield(get = "getter_type")]: Override the default getter configuration.

Example:

use datastruct::DataStruct;

#[derive(DataStruct)]
#[dstruct(get)] // equivalent to `get = "get"`
struct Data {
    auto_get: usize,
    #[dfield(get = "no")]
    no_get: usize,
    #[dfield(get = "full")]
    can_move: usize,
}

// generated code
impl Data {
    pub fn auto_get(&self) -> &usize {
        &self.auto_get
    }
    pub fn can_move(&self) -> &usize {
        &self.can_move
    }

    pub fn get_can_move(self) -> usize {
        self.can_move
    }
}

map

Map a field’s value and modify the structure. This does not have structure-level configuration.

Field Configuration:

• #[dfield(map)] | #[dfield(map = ture): Enable mapping.
• #[dfield(map = false)]: Disable mapping. Typically, you don’t need to explicitly disable mapping since it’s the default behavior.

Examples:

use datastruct::DataStruct;

#[derive(DataStruct)]
struct MapItem {
    #[dfield(map)] // equivalent to `#[dfield(map = true)]
    item: usize,
}

// generated code
impl MapItem {
    pub fn map_item(mut self, f: impl FnOnce(usize) -> usize) -> Self {
        self.item = f(self.item);
        self
    }
}

do_with

Modify a field’s value. This does not have structure-level configuration.

Field Configuration:

• #[dfield(do_with)] | #[dfield(do_with = ture): Enable do_with.
• #[dfield(do_with = false)]: Disable do_with. Typically, you don’t need to explicitly disable mapping since it’s the default behavior.

Examples:

use datastruct::DataStruct;

#[derive(DataStruct)]
struct MapItem {
    #[dfield(do_with)] // equivalent to `#[dfield(do_with = true)]
    item: usize,
}

// generated code
impl MapItem {
    pub fn do_with_item(&mut self, f: impl FnOnce(&mut usize)) {
        f(&mut self.item);
    }
}

Comparison cmp

Macro-generateable comparison traits are Eq, PartialEq, Ord and PartialOrd.

Syntax:

All cmp configurations must be defined within cmp(xxx) field:

#[dstruct(cmp(<your config>))]
#[dfield(cmp(<your config>))]

Eq and PartialEq

Syntax:

• #[dstruct(cmp(eq))]: Generate Eq implementation for the struct. Note that this won’t implement PartialEq, and you must explicitly enable that.
• #[dfield(cmp(peq))] | #[dfield(cmp(partial_eq))]: Generate PartialEq implementation for the struct.

Field Configuration:

• #[dfield(cmp(eq))]: When checking equality, this field is included. (Default if enabled.)
• #[dfield(cmp(eq = boolean))]: Whether to include this field in equality check.

Examples:

use datastruct::DataStruct;

#[derive(DataStruct)]
#[dstruct(cmp(eq, peq))]
struct CanEq {
    // #[dfield(cmp(eq))]
    // you don't need to explicitly specify this.
    content: usize,
    #[dfield(cmp(eq = false))]
    do_not_check: usize,
}

// generated code
impl ::std::cmp::PartialEq for CanEq {
    fn eq(&self, rhs: &Self) -> bool {
      (self.content == rhs.content)
    }
}
impl ::std::cmp::Eq for CanEq {}

Ord and PartialOrd

Syntax:

• #[dstruct(ord)]: Implement Ord for the struct.
• #[dstruct(pord)] | #[dstruct(partial_ord)]: Implement PartialOrd for the struct.

Field Configuration:

• Ord: The configuration key is cmp or ord. (Disabled by default.)

  • #[dfield(cmp(ord))]: Include this field in the Ord implementation.

  • #[dfield(cmp(ord = boolean))]: Whether to include this field in the Ord implementation.

  • #[dfield(cmp(ord = "isize"))] | #[dfield(cmp(ord = isize))]: Set the sequence of the field in the Ord implementation.

    By default, all included fields’ comparison results are chained with Ordering::then_with. This configuration can change the index of the field. Negative number is allowed to use.

• PartialOrd: The configuration key is pcmp, partial_cmp, pord or partial_ord. (Disabled by default.)

  • #[dfield(cmp(pord))]: Include this field in the PartialOrd implementation.

  • #[dfield(cmp(pord = boolean))]: Whether to include this field in the PartialOrd implementation.

  • #[dfield(cmp(pord = "isize"))] | #[dfield(cmp(pord = isize))]: Set the sequence of the field in the PartialOrd implementation.

    By default, all included fields’ comparison results are chained with Option::and_then and Ordering::then_with. This configuration can change the index of the field. Negative number is allowed to use.

Note:

• If no field is configured to be included, then Ord and PartialOrd will not be implemented.
• If both Ord and PartialOrd are enabled:
  • If only Ord is configured, then PartialOrd will be simply Some(Ord).
  • If both are configured, Clippy may throw a clippy::non_canonical_partial_ord_impl (non-canonical implementation of partial_cmp on an Ord type) warning about the implementation, see Clippy Lint for more information.

Examples:

use datastruct::DataStruct;

#[derive(DataStruct)]
#[dstruct(cmp(eq, peq, ord, pord))]
struct MyComparable {
    #[dfield(cmp(ord))]
    only_ord: usize,
    #[dfield(cmp(pord))]
    only_partial_ord: usize,
    #[dfield(cmp(ord = -1, pord = -1))]
    both_ord: usize,
}

// generated code (`Eq` and `PartialEq` is omitted).

impl ::std::cmp::Ord for MyComparable {
    fn cmp(&self, other: &Self) -> ::std::cmp::Ordering {
        self.both_ord
            .cmp(&other.both_ord)
            .then_with(|| self.only_ord.cmp(&other.only_ord))
    }
}

impl ::std::cmp::PartialOrd for MyComparable {
    fn partial_cmp(&self, other: &Self) -> ::core::option::Option<::std::cmp::Ordering> {
        self.both_ord
            .partial_cmp(&other.both_ord)
            // the following identifier `__gen_xxx` is generated by the macro
            .and_then(|__gen_dparord| {
                self.only_partial_ord
                    .partial_cmp(&other.only_partial_ord)
                    .map(|__gen_dparord_self| __gen_dparord.then(__gen_dparord_self))
            })
    }
}

Operations ops

Macro-generateable operation traits are Add +, Sub -, Mul *, Div / and their assignable versions AddAssign +=, SubAssign -=, MulAssign *= and DivAssign /=.

Syntax:

All ops configurations must be defined within ops(xxx) field:

#[dstruct(ops(<your config>))]
#[dfield(ops(<your config>))]

Operations definitions on structure-level can be declared by #[dstruct(ops(add = "type"))] (Take Add/AddAssign as an example):

• “both” | “all”: Generate both assignment and plain operation for all fields by default.
• “assign”: Only generate assignment by default.
• “plain” | “default”“: Generate plain operation by default. (Default if enabled.)

Field Configuration:

• Plain operations + - * /: (Take Add + as an example:)
  • #[dfield(ops(add = "type"))]:
    • “inherit” | “default”: Inherit the default configuration declared in the dstruct attributes.
    • “ignore” | “no”: Ignore this field, that is, A1 + A2 -> A1.
  • #[dfield(ops(add = boolean))]: Whether to include this field.
  • #[dfield(ops(add = "expression"))]: Use your own expression to implement the Add.
• Assignment operations += -= *= /=: (Take AddAssign += as an example:)
  • #[dfield(ops(add_assign = "type"))]:
    • “inherit” | “default”: Inherit the default configuration declared in the dstruct attributes.
    • “ignore” | “no”: Ignore this field, that is, self.A <- self.A.
  • #[dfield(ops(add_assign = boolean))]: Whether to include this field.
  • #[dfield(ops(add_assign = "expression"))]: Use your own expression to implement the AddAssign.

About expression:

You can use your expression to manually implement the operations. The expression must be wrapped in a literal string. Use $self to refer to the left-hand self value, and use $rhs to refer to the right-hand other value.

For example,

#[dfield(ops(add = "$self.something + $rhs.otherthing"))]
field: SomeType

will be translated into

Self {
    field: self.something + other.otherthing,
    ..
}

Examples:

use datastruct::DataStruct;

#[derive(Debug, Clone, Copy, DataStruct)]
#[dstruct(ops(add = "both"))]
struct CanOpsAssign {
    can_add: i8,
    #[dfield(ops(add = "ignore"))]
    no_add: i8,
    #[dfield(ops(add_assign = "std::cmp::max($self.max, $rhs.max)"))]
    max: i8,
    #[dfield(ops(add_assign = "std::cmp::min($self.min, $rhs.min)"))]
    min: i8,
}

// generated code
impl ::std::ops::Add for CanOpsAssign {
    type Output = Self;
    fn add(self, rhs: Self) -> Self {
        Self {
            can_add: self.can_add + rhs.can_add,
            no_add: self.no_add,
            max: self.max + rhs.max,
            min: self.min + rhs.min,
        }
    }
}

impl ::std::ops::AddAssign for CanOpsAssign {
    fn add_assign(&mut self, rhs: Self) {
        self.can_add += rhs.can_add;
        self.no_add += rhs.no_add;
        self.max = std::cmp::max(self.max, rhs.max);
        self.min = std::cmp::min(self.min, rhs.min);
    }
}

Traits

ConstDataStruct

The macro’s const option will implement this trait for the structure.

DataStruct

The macro’s default option will implement this trait for the structure.

Derive Macros

DataStruct