Is there any way to get an XCode build setting to vary according to build ACTION (e.g. clean, rebuild)?

Question

I'm trying to figure out exactly how schemes work in xcode and what they're for. I have a cross-platform product that's built on OS X using an external build system ( scons ). I'd like to be able to build/debug it from Xcode, mostly because of the symbol search and the debugger. I've been using eclipse CDT which mostly works well, but has some quirks.

I can mostly get this to work by creating an empty project and adding an 'external build system' target. Then, as part of the 'Info' of the target, I specify the 'Build Tool' as /usr/local/bin/scons, and the 'Arguments' are the build parameters that I send to scons. Basically I have the following build variables called $(TARGET) and $(BUILD_TYPE) that vary according to whether the build is debug or release, so those can be specified as conditional 'Build Settings'.

The problem is I'd like Menu->Project->Clean to work. It looks like Xcode/xcodebuilder use the $(ACTION) variable to pass this on - where $(ACTTION) is either 'build', 'clean', or some other build actions. See xcodebuild ACTION. Scons is a bit different - it has a built-in clean action that's invoked on the command line with scons -c. So my first thought was to use a conditional 'Build Setting' to pass this parameter, but it turns out that conditional 'Build Settings' don't seem to vary based on the build ACTION - just the build architecture and SDK.

Is it possible to add an expression to a 'Build Setting' in Xcode/xcodebuilder? Is there another good way that I could get 'Clean' to work in Xcode with scons?

Answer 1

Write a wrapper script for SCons, and put it in your project. For example:

External Build Tool Configuration

• Build Tool: $(PROJECT_DIR)/scons-xcode-wrapper.sh
• Arguments: $(ACTION)

Wrapper Script

From an experiment, it looks like $(ACTION) is empty when building, and set to clean when cleaning.

#!/bin/sh
cd "$PROJECT_DIR"
case $1 in
  clean)
    scons -c
    ;;
  *)
    scons
    ;;
esac

Don't forget to chmod +x your script.