usingnamespace

usingnamespace is a top level declaration that imports all the public declarations of the operand, which must be a struct, union, or enum, into the current scope:

usingnamespace.zig

  1. usingnamespace @import("std");
  2. test "using std namespace"{
  3. debug.assert(true);
  4. }
  1. $ zig test usingnamespace.zig
  2. 1/1 test "using std namespace"...OK
  3. All1 tests passed.

Instead of the above pattern, it is generally recommended to explicitly alias individual declarations. However, 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:

  1. pub usingnamespace @cImport({
  2. @cInclude("epoxy/gl.h");
  3. @cInclude("GLFW/glfw3.h");
  4. @cDefine("STBI_ONLY_PNG","");
  5. @cDefine("STBI_NO_STDIO","");
  6. @cInclude("stb_image.h");
  7. });

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.