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Swift Variable Injector

license Build Status Swift Xcode SPM

Variable injector is a very simple project with the goal of inject CI pipelines environment variables values into Swift code static values before compilation and Continuous deployment to a specific environment(Development, Testing or Production) where we can define the values injected for each build and deployment e.g. an API URL that the App uses and is different for each environment. Also, it allows us to not expose our production keys and values in statically in our code.

The project uses SwiftSyntax to perform a reliable substitutions of static literal strings with the CI environment variables values.


Manually Download

We can manually download the binary from the releases and export to the path on the CI pipeline

cd /tmp
curl -OL
cp -f ./x86_64-apple-macosx/release/variable-injector /usr/local/bin/variable-injector

rm ./
rm -rf ./x86_64-apple-macosx
rm -rf ./__MACOSX/


To install the lastest version just run the

curl -ssl | sh

Or just clone the repo and run make install

With that installed and on our bin folder, now we can use it.


For a detailed example of using this, check out the article Continuous Integration Environment Variables in iOS projects using Swift on Medium.

Note If you having issues with Xcode11 use the version 0.3.3 of the tool.

You should have a class or struct with your envirionment variables declaration following the $(VAR_NAME) pattern. Example:

   struct CI {
      static var serviceAPIKey: String = "$(SERVICE_PROD_KEY)"
      static var otherAPIKey: String = "$(OTHER_PROD_KEY)"

With the environments static declarations matching the pattern

variable-injector --file ${SRCROOT}/Envirionment/CI.swift 

If environment variables with those names, as in the example you have the SERVICE_PROD_KEY and OTHER_PROD_KEY are defined on the build machine for this pipeline the injector you replace the string literal with the envirionment variable value.

Example of the file after the substitution.

   struct CI {
      static var serviceAPIKey: String = "h344hjk2h4j3h24jk32h43j2k4h32jk4hkj324h"
      static var otherAPIKey: String = "dsa76d7adas7d6as87d6as78d6aklre423s7d6as8d7s6"

Using as Run Script in Build Phases

You can add the script call for variable replacement on your build phases. We just have setup our Development keys in our local machine as environment variables and build the project.

Important: Is very important to add this Run Script phase before the Compile Sources phase. So the variables will be replaced and then compiled :))

if which variable-injector >/dev/null; then
  variable-injector --file ${SRCROOT}/YourProject/YourGroupFolderPath/File.swift --verbose # Pass your paramenters
  echo "Warning: Swift Variable Injector not installed, download from"


We can ignore patterns that match $(ENV_VAR) to avoid the replace.

variable-injector --file ${SRCROOT}/Envirionment/CI.swift --ignore OTHER_PROD_KEY

And also, to see the logs of variables, values and source output you can use --verbose

IMPORTANT The verbose mode you print the values of your environment variables on the logs. So you may be careful and use it only for debug porpuses.

variable-injector --file ${SRCROOT}/Envirionment/CI.swift --verbose

After that we can just proceed to the build, archive and other steps of our CI/CD pipeline.


Variable Injector is released under the MIT License.

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