usingnamespace

usingnamespace is a declaration that mixes all the public declarations of the operand, which must be a struct, union, enum, or opaque, into the namespace:

usingnamespace.zig

test "using std namespace" {
    const S = struct {
        usingnamespace @import("std");
    };
    try S.testing.expect(true);
}

Shell

$ zig test usingnamespace.zig
1/1 test "using std namespace"... OK
All 1 tests passed.

usingnamespace has an important use case when organizing the public API of a file or package. For example, one might have c.zig with all of the C imports:

c.zig

pub usingnamespace @cImport({
    @cInclude("epoxy/gl.h");
    @cInclude("GLFW/glfw3.h");
    @cDefine("STBI_ONLY_PNG", "");
    @cDefine("STBI_NO_STDIO", "");
    @cInclude("stb_image.h");
});

The above example demonstrates using pub to qualify the usingnamespace additionally makes the imported declarations pub. This can be used to forward declarations, giving precise control over what declarations a given file exposes.