Nim如何检查环境是否在生产中？

Question

Is there any convention for flagging a production env in Nim?
Like process.env.NODE_ENV === 'production' in JavaScript for instance.
Or should I use pragmas like

when defined(release):

Answer 1

The when defined(release) line only checks at compile time if you are building a binary for release/non release, which is a compile time symbol you get by compiling your source code with the -d:release switch. As such, this is not telling you anything about the runtime environment at all, but about the compilation. You could compile both debug/release binaries and use them both in production, maybe because you have a crash and need to replace your release binary with a debug version to get a meaningful stack trace/explanation.

These compile time symbols are usually embedded through the use of an external script/build machinery, like NimScript , Nimble , nake , or just a simple .bat/.sh file.

A line like process.env.NODE_ENV === 'production' from javascript probably comes from somewhere , be it a static file in your project or something else. You need to figure out what exactly defines your runtime environment in production and add the Nim code necessary to detect that difference. For instance, your Nim program could run at startup a GET JSON query against a server you own and parse a isProduction: true value somewhere. This server could be parametrised in a configuration file where end users specify the environment they are actually running (or just avoid servers and read a local configuration file).

Or if you like the compile time symbols, you could have a shell script that builds your binary N times for as many different environments you want to have through the use of user-defined pragmas (and then you need to be careful about using the appropriate binary where applicable).