#containers #associative #macro #container #proc-macro #procedural-macro #struct #key #btreemap #convert

struct2map

Procedural macro library for converting between Rust structs and associative containers

1 unstable release

0.1.6 Oct 11, 2022

#494 in Rust patterns

MIT license

10KB
102 lines

structmap

Actions crates.io version Docs

Procedural macro crate for converting between Rust struct types and associative containers.

use std::collections::BTreeMap;
// converting between a struct like ...
struct SomeData {
    key: String
}

// ... and a BTreeMap like ...
let somedata_hm: BTreeMap<String, String> = BTreeMap::new();

This removes the need to pattern match on attributes and keys when making a conversion.

This was largely inspired by previous work done by @Ameobea, but extends on it much further to support conversion both ways, generic value types, and Rust 2018 conventions.

Usage

In your Cargo.toml file, include the crate as so:

[dependencies]
structmap = "0.1"

Now let's demonstrate conversion! Note that your struct type should extend the Default trait for type conversion to account for uninitialized attributes.

structmap supports conversion between two types of map aliases:

  1. StringMap - Strings for both keys and values. Conversion is supported only one-way at the moment from struct to BTreeMap, but not the other way around.
  2. GenericMap - Generic serde-style Values as values. Conversion is supported both ways, but limited.

Map to Struct

use structmap::FromMap;
use structmap_derive::FromMap;

#[derive(FromMap)]
struct TestStruct {
    name: String,
    value: i64,
}

impl Default for TestStruct {
    fn default() -> Self {
        Self {
            name: String::new(),
            value: 0
        }
    }
}

fn main() {
	// create a hashmap with key-value pairs
    let mut hm = GenericMap::new();

    // `Value` is an enum wrapper to support genericized types, to support structs
    // with varying types for their fields.
    hm.insert(String::from("name"), Value::new(String::from("example")));
    hm.insert(String::from("value"), Value::new(0_i64));

    // convert hashmap to struct, and check attributes
    let test: TestStruct = TestStruct::from_genericmap(hm);
    assert!(test.name == "example");
    assert!(test.value == 0);
}

Struct to Map

use structmap::{ToMap, value::Value};
use structmap_derive::ToMap;
use std::collections::BTreeMap;

#[derive(ToMap, Default)]
struct TestStruct {
    name: String,
    value: i64,
}

// impl Default ...

fn main() {
    let test_struct = TestStruct {
        name: String::from("example"),
        value: 0,
    };

    // convert struct to generic map, and check attributes
    let hm: BTreeMap<String, Value> = TestStruct::to_genericmap(test_struct);
    assert!(hm.get("name").unwrap().string().unwrap() == "example");
    assert!(hm.get("value").unwrap().i64().unwrap() == 0);

    let test_struct = TestStruct {
        name: String::from("example"),
        value: 0,
    };

    // convert struct to string map, and check attributes
    let hm: BTreeMap<String, String> = TestStruct::to_stringmap(test_struct);
    assert!(hm.get("name").unwrap() == "example");
    assert!(hm.get("value").unwrap() == "0");
}

Need a different key name when converting from a struct to a map container? Use #[rename] for struct attributes!

use structmap::ToMap;
use structmap_derive::ToMap;

#[derive(ToMap, Default)]
struct TestStruct {
    #[rename(name = "Full Name")]
    name: String,

    #[rename(name = "Data")]
    value: String,
}

Contributions

All complex types, include dynamic arrays, Options, Results and data structures are not yet supported (which you can help implement!).

Feel free to let me know if there are any outstanding features that should be implemented!

License

MIT License

Dependencies

~210–610KB
~15K SLoC