Namespace

Namespaces provide essential structure and clarity to your Rell projects, allowing for better organization and modularization of code.

Namespaces have the following characteristics:

• Simplified referencing: Within a namespace, you can use identifiers directly without specifying the full name. For example, use country instead of foo.country when inside the foo namespace.
• Qualified table names: Tables for entities and objects defined in a namespace include the full namespace path in their names. For instance, the table for entity foo.user is named c0.foo.user.
• Multiple definitions: You can define a namespace with the same name multiple times, each with different inner definitions, allowing for distributed declarations across files.

Basic namespace usage

namespace foo {
    entity user {
        name;
        country;
    }

    struct point {
        x: integer;
        y: integer;
    }

    enum country {
        USA,
        DE,
        FR
    }
}

query get_users_by_country(c: foo.country) = foo.user @* { .country == c };

Anonymous namespaces

Anonymous namespaces allow for focused organization or applying annotations to a group of definitions without creating a named namespace.

Example

namespace {
    // some definitions
}

You can use it to apply an annotation to a set of definitions:

@mount('foo.bar')
namespace {
    entity user {}
    entity company {}
}

Nested namespaces

Create hierarchical structures using nested namespaces for fine-grained organization. You can use nested namespaces for complex projects with multiple layers of organization.

Short notation:

namespace x.y.z {
        function f() = 123;
}

Equivalent expanded notation:

namespace x {
    namespace y {
        namespace z {
            function f() = 123;
        }
    }
}

Splitting namespaces across files

For improved modularity, you can distribute namespace members across multiple files within a module. When splitting namespaces across files, ensure consistent naming and organization.

Example

// lib/a.rell
namespace ns {
    function f(): integer = 123;
}

// lib/b.rell
namespace ns {
    function g(): integer = 456;
}

// main.rell
import .lib;

function main() {
    print(lib.ns.f()); // Outputs: 123
    print(lib.ns.g()); // Outputs: 456
}