| ... | @@ -4862,14 +4862,41 @@ fn deferErrorExample(is_error: bool) !void { | ... | @@ -4862,14 +4862,41 @@ fn deferErrorExample(is_error: bool) !void { |
| 4862 | print("encountered an error!\n", .{}); | 4862 | print("encountered an error!\n", .{}); |
| 4863 | } | 4863 | } |
| 4864 | | 4864 | |
| | 4865 | // inside a defer method the return statement |
| | 4866 | // is not allowed. |
| | 4867 | // The following lines produce the following |
| | 4868 | // error if uncomment |
| | 4869 | // ``` |
| | 4870 | // defer.zig:73:9: error: cannot return from defer expression |
| | 4871 | // return error.DeferError; |
| | 4872 | // ``` |
| | 4873 | // |
| | 4874 | //defer { |
| | 4875 | // return error.DeferError; |
| | 4876 | //} |
| | 4877 | |
| 4865 | if (is_error) { | 4878 | if (is_error) { |
| 4866 | return error.DeferError; | 4879 | return error.DeferError; |
| 4867 | } | 4880 | } |
| 4868 | } | 4881 | } |
| 4869 | | 4882 | |
| | 4883 | // The errdefer keyword support also an alternative syntax to capture the |
| | 4884 | // error generated in case of one error. |
| | 4885 | // |
| | 4886 | // This is useful when during the clean up after an error additional |
| | 4887 | // message want to be printed. |
| | 4888 | fn deferErrorCaptureExample() !void { |
| | 4889 | errdefer |err| { |
| | 4890 | std.debug.print("the error is {s}\n", .{@errorName(err)}); |
| | 4891 | } |
| | 4892 | |
| | 4893 | return error.DeferError; |
| | 4894 | } |
| | 4895 | |
| 4870 | test "errdefer unwinding" { | 4896 | test "errdefer unwinding" { |
| 4871 | deferErrorExample(false) catch {}; | 4897 | deferErrorExample(false) catch {}; |
| 4872 | deferErrorExample(true) catch {}; | 4898 | deferErrorExample(true) catch {}; |
| | 4899 | deferErrorCaptureExample() catch {}; |
| 4873 | } | 4900 | } |
| 4874 | {#code_end#} | 4901 | {#code_end#} |
| 4875 | {#see_also|Errors#} | 4902 | {#see_also|Errors#} |
| ... | @@ -11930,7 +11957,7 @@ fn readU32Be() u32 {} | ... | @@ -11930,7 +11957,7 @@ fn readU32Be() u32 {} |
| 11930 | <pre>{#syntax#}errdefer{#endsyntax#}</pre> | 11957 | <pre>{#syntax#}errdefer{#endsyntax#}</pre> |
| 11931 | </th> | 11958 | </th> |
| 11932 | <td> | 11959 | <td> |
| 11933 | {#syntax#}errdefer{#endsyntax#} will execute an expression when control flow leaves the current block if the function returns an error. | 11960 | {#syntax#}errdefer{#endsyntax#} will execute an expression when control flow leaves the current block if the function returns an error, the errdefer expression can capture the unwrapped value. |
| 11934 | <ul> | 11961 | <ul> |
| 11935 | <li>See also {#link|errdefer#}</li> | 11962 | <li>See also {#link|errdefer#}</li> |
| 11936 | </ul> | 11963 | </ul> |
Andrew Kelley <andrew@ziglang.org> 2022-09-14 19:26:28-04:00
GitHub <noreply@github.com> 2022-09-14 19:26:28-04:00
Signed by PGP key 4AEE18F83AFDEB23