structmap

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

// converting between a struct like ...
struct SomeData {
    key: String
}

// ... and a BTreeMap like ...
let somedata_hm = 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(FromBTreeMap)]
struct TestStruct {
    name: String,
    value: i32,
}

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));

    // 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;
use structmap_derive::ToMap;

#[derive(ToBTreeMap)]
struct TestStruct {
    name: String,
    value: i32,
}

// 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().i32().unwrap() == 0);

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

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

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

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

Limitations

At the current moment, Value only supports encapsulate basic primitive types, which includes the following:

• i32 and u32 numerals
• bools
• Strings and &strs

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

Contributions

This is still a WIP crate, and will mostly be used for personal projects, but feel free to let me know if there are any outstanding features that should be implemented!

License

MIT License