| ... | ... | @@ -5187,6 +5187,41 @@ test "@intToPtr for pointer to zero bit type" { |
| 5187 | 5187 | </p> |
| 5188 | 5188 | {#header_close#} |
| 5189 | 5189 | |
| 5190 | {#header_open|usingnamespace#} |
| 5191 | <p> |
| 5192 | {#syntax#}usingnamespace{#endsyntax#} is a top level declaration that imports all the declarations of |
| 5193 | the operand, which must be a {#link|struct#}, {#link|union#}, or {#link|enum#}, into the current scope: |
| 5194 | </p> |
| 5195 | {#code_begin|test|usingnamespace#} |
| 5196 | usingnamespace @import("std"); |
| 5197 | |
| 5198 | test "using std namespace" { |
| 5199 | debug.assert(true); |
| 5200 | } |
| 5201 | {#code_end#} |
| 5202 | <p> |
| 5203 | Instead of the above pattern, it is generally recommended to explicitly alias individual declarations. |
| 5204 | However, {#syntax#}usingnamespace{#endsyntax#} has an important use case when organizing the public |
| 5205 | API of a file or package. For example, one might have <code>c.zig</code> with all of the |
| 5206 | {#link|C imports|Import from C Header File#}: |
| 5207 | </p> |
| 5208 | <pre>{#syntax#} |
| 5209 | pub usingnamespace @cImport({ |
| 5210 | @cInclude("epoxy/gl.h"); |
| 5211 | @cInclude("GLFW/glfw3.h"); |
| 5212 | @cDefine("STBI_ONLY_PNG", ""); |
| 5213 | @cDefine("STBI_NO_STDIO", ""); |
| 5214 | @cInclude("stb_image.h"); |
| 5215 | }); |
| 5216 | {#endsyntax#}</pre> |
| 5217 | <p> |
| 5218 | The above example demonstrates using {#syntax#}pub{#endsyntax#} to qualify the |
| 5219 | {#syntax#}usingnamespace{#endsyntax#} additionally makes the imported declarations |
| 5220 | {#syntax#}pub{#endsyntax#}. This can be used to forward declarations, giving precise control |
| 5221 | over what declarations a given file exposes. |
| 5222 | </p> |
| 5223 | {#header_close#} |
| 5224 | |
| 5190 | 5225 | {#header_open|comptime#} |
| 5191 | 5226 | <p> |
| 5192 | 5227 | Zig places importance on the concept of whether an expression is known at compile-time. |
Andrew Kelley <andrew@ziglang.org> 2019-09-24 21:23:12-04:00
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