ActivityStreams

A set of Traits and Types that make up the ActivityStreams and ActivityPub specifications

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Usage

First, add ActivityStreams to your dependencies

activitystreams = "0.6.2"

Types

The project is laid out by Kind => vocabulary => Type

So to use an ActivityStreams Video, you'd write

use activitystreams::object::streams::Video;

And to use an ActivityPub profile, you'd write

use activitystreams::object::apub::Profile;

Link is a little different, since there's only one defined link type, called Mention.

use activitystreams::link::Mention;

Properties

Each concrete type implements AsRef<> for each of their properties fields. A basic ActivityStreams object will implement AsRef<ObjectProperties>, while an ActivityPub Actor might implement AsRef<ObjectProperties>, AsRef<ApObjectProperties>, and AsRef<ApActorProperties>.

The Properties types can be found near the kind they're associated with. ObjectProperties and ApObjectProperties are located in activitystreams::object::properties.

The Properties types are generated by the properties macro, which attempts to create fields that represent exactly the bounds of the ActivityStreams and ActivityPub specifications.

For example, the Object type in ActivityStreams has a summary field, which can either be represented as an xsd:string or an rdf:langString. It also states that the summary field is not functional, meaning that any number of xsd:string or rdf:langString, or a combination thereof, can be present. To represent this, the properties macro generates a couple enum types.

First, it generates ObjectPropertiesSummaryTermEnum, which is a "terminating" enum. "terminating" in this context means it is the smallest unit of the type. This enum has two variants, named after the types they contain, XsdString(...) and RdfLangString(...).

Next, it generates ObjectPropertiesSummaryEnum, which contains two variants, Term(...) and Array(...). The Term variant contains an ObjectPropertiesSummaryTermEnum, and the Array variant contains a Vec<ObjectPropertiesSummaryTermEnum>.

Finally, when declaring the field, it generates summary: Option<ObjectPropertiesSummaryEnum>, since summary is not a required field.

This resulting type is exactly specific enough to match the following valid ActivityStreams json, without matching any invalid json.

With no summary:

{}

With a sring summary:

{
    "summary": "A string"
}

With an rdf langstring

{
    "summary": {
        "@value": "A string",
        "@language": "en"
    }
}

With multiple values

{
    "summary": [
        {
            "@value": "A string",
            "@language": "en"
        },
        "An xsd:string this time"
    ]
}

It may seem like interacting with these types might get unweildy, so the properties macro also generates methods for interacting with each field.

fn set_summary_xsd_string<T>(&mut self, T) -> Result<...>;
fn set_summary_rdf_lang_string<T>(&mut self, T) -> Result<...>;
fn set_many_summary_xsd_strings<T>(&mut self, Vec<T>) -> Result<...>;
fn set_many_summary_rdf_lang_strings<T>(&mut self, Vec<T>) -> Result<...>;

fn delete_summary(&mut self) -> &mut Self;

fn get_summary_xsd_string(&self) -> Option<XsdString>;
fn get_summary_rdf_lang_string(&self) -> Option<RdfLangString>;
fn get_many_summary_xsd_strings(&self) -> Option<Vec<&XsdString>>;
fn get_many_summary_rdf_lang_strings(&self) -> Option<Vec<&RdfLangString>>;

These methods provide access to setting and fetching uniformly typed data, as well as deleting the data. In the setter methods, the type parameter T is bound by TryInto<XsdString> or TryInto<RdfLangString>. This allows passing values to the method that can be converted into the types, rather than requiring the caller to perform the conversion.

Types like XsdString and RdfLangString can be found in the primitives module. Unless you're building your own custom types, you shouldn't need to import them yourself. They each implement FromStr for parsing and Display to convert back to strings, as well as From and Into or TryFrom and TryInto for types you might expect them to (e.g. XsdNonNegativeInteger implements From<u64> and Into<u64>).

For some fields, like id, there is only one valid type. methods generated for fields like these will leave out the type name from the function name.

fn set_id<T>(&mut self, T) -> Result<...>;
fn delete_id(&mut self) -> &mut Self;
fn get_id(&self) -> Option<XsdAnyUri>;

Traits

This library provides a number of traits, such as Object, Link, Actor, Activity, Collection, and CollectionPage. The majority of these traits exist solely to "mark" types, meaning they don't provide value, at runtime, but exist to add constraints to generics at compiletime.

If you want to make a function that manipulates an Activity, but not a normal object, you could bound the function like so:

fn my_manipulator<T>(some_activity: T) -> Result<&mut ObjectProperties, SomeErrorType>
where
    T: Activity + AsMut<ObjectProperties>,
{
    some_activity.as_mut().set_whatever_tbh()
}

Kinds

This library has a set of unit structs that serialize and deserialize to strings. This is to enable different ActivityPub Object types to be deserialized into different Named structs. These can be found in activitystreams::objects::kind, and similar paths.

To build your own Person struct, for example, you could write

use activitystreams::actor::kind::PersonType;

#[derive(serde::Deserialize, serde::Serialize)]
pub struct MyPerson {
    // Do a rename since `type` is not a valid rust field name
    #[serde(rename = "type")]
    kind: PersonType,
}

And this type would only deserialize for JSON where "type":"Person"

Features

There are a number of features that can be disabled in this crate. By default, everything is enabled.

activitystreams = { version = "0.6.2", default-features = "false", features = ["derive"] }

feature	what you get
none	Just the Marker Traits
derive	Marker Traits + derive macros from activitystreams-derive
kinds	Marker Traits + derive macros + Kind UnitStructs
primitives	Marker Traits + Primitive values
types	Everything, this is the default

Examples

Basic

use activitystreams::object::{streams::Video, properties::ObjectProperties};
use anyhow::Error;

// We perform configuration in a dedicated function to specify which Properties type we want to
// perform the operations on.
fn configure_video(mut v: impl AsMut<ObjectProperties>) -> Result<(), Error> {
    v.as_mut()
        .set_context_xsd_any_uri("https://www.w3.org/ns/activitystreams")?
        .set_id("https://example.com/@example/lions")?
        .set_url_xsd_any_uri("https://example.com/@example/lions/video.webm")?
        .set_name_xsd_string("My Cool Video")?
        .set_summary_xsd_string("A video about some cool lions")?
        .set_media_type("video/webm")?
        .set_duration("PT4M20S")?;

    Ok(())
}

fn main() -> Result<(), Error> {
    let mut v = Video::default();

    configure_video(&mut v)?;

    println!("Video, {:#?}", v);

    let s = serde_json::to_string(&v)?;

    println!("json, {}", s);

    let v: Video = serde_json::from_str(&s)?;

    println!("Video again, {:#?}", v);

    Ok(())
}

Intermediate

use activitystreams::{
    context,
    actor::{Actor, ActorBox},
    object::{
        properties::{
            ObjectProperties,
            ProfileProperties
        },
        apub::Profile,
        Object, ObjectBox,
    },
    primitives::XsdAnyUri,
    PropRefs,
};
use serde::{Deserialize, Serialize};
use std::any::Any;

#[derive(Clone, Debug, Default, Deserialize, Serialize, PropRefs)]
#[serde(rename_all = "camelCase")]
#[prop_refs(Object)]
#[prop_refs(Actor)]
pub struct Persona {
    #[serde(rename = "@context")]
    context: XsdAnyUri,

    #[serde(rename = "type")]
    kind: String,
}

fn main() -> Result<(), anyhow::Error> {
    let mut profile = Profile::default();

    let pprops: &mut ProfileProperties = profile.as_mut();

    pprops.set_describes_object_box(Persona {
        context: context(),
        kind: "Persona".to_owned(),
    })?;

    let oprops: &mut ObjectProperties = profile.as_mut();
    oprops.set_context_xsd_any_uri(context())?;

    let profile_string = serde_json::to_string(&profile)?;

    let profile: Profile = serde_json::from_str(&profile_string)?;

    Ok(())
}

Advanced

use activitystreams::{
    properties,
    link::{
        properties::LinkProperties,
        Link, LinkBox, Mention,
    },
    PropRefs, UnitString,
};
use serde::{Deserialize, Serialize};

/// Using the UnitString derive macro
///
/// This macro implements Serialize and Deserialize for the given type, making this type
/// represent the string "MyLink" in JSON.
#[derive(Clone, Debug, Default, UnitString)]
#[unit_string(MyLink)]
pub struct MyKind;

properties! {
    My {
        docs [ "Defining our own properties struct called MyProperties" ],

        required_key {
            docs [
                "Our own required key field",
                "",
                "'types' defines the range of values that can be stored in required_key",
                "",
                "'functional' means there is at most one value for required_key",
                "'required' means there is at least one value for required_key",
            ],
            types [ String ],
            functional,
            required,
        },
    }
}

/// Using the Properties derive macro
///
/// This macro generates getters and setters for the associated fields.
#[derive(Clone, Debug, Default, Deserialize, Serialize, PropRefs)]
#[serde(rename_all = "camelCase")]
#[prop_refs(Link)]
pub struct My {
    /// Use the UnitString MyKind to enforce the type of the object by "MyLink"
    pub kind: MyKind,

    /// Derive AsRef/AsMut for My -> MyProperties
    #[prop_refs]
    pub my_properties: MyProperties,

    /// Derive AsRef/AsMut/Link for My -> LinkProperties
    #[prop_refs]
    pub link_properties: LinkProperties,
}

fn main() -> Result<(), anyhow::Error> {
    let mut my_link = My::default();

    let lprops: &mut MyProperties = my_link.as_mut();
    lprops.set_required_key("Hey")?;

    let my_link_string = serde_json::to_string(&my_link)?;

    let my_link: My = serde_json::from_str(&my_link_string)?;

    Ok(())
}

Contributing

Feel free to open issues for anything you find an issue with. Please note that any contributed code will be licensed under the GPLv3.

License

Copyright © 2018 Riley Trautman

ActivityStreams is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

ActivityStreams is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. This file is part of ActivityStreams.

You should have received a copy of the GNU General Public License along with ActivityStreams. If not, see http://www.gnu.org/licenses/.