See here

You can now install EiffelStudio via the Homebrew package manager. See Eiffel On Mac. In brief:

• install XCode
• install XQuartz
• install brew
• run the following commands:

brew update
brew tap homebrew/x11
brew install eiffelstudio

The final steps will take quite a bit of time since we are recompiling the whole EiffelStudio delivery. Once done, you will have access to `ec', `estudio', and other executables in your path without having to set any of the ISE_EIFFEL or ISE_PLATFORM environment variables (they are automatically set for you when you launch those programs).

Until a Homebrew package is available do the following. It will take some time to update Macports:

• Make sure you have the latest Xcode and Macports
• Update Macports for Yosemite. Download it here.

sudo port -v selfupdate
sudo port upgrade outdated

• Download the latest EiffelStudio for MacOs here (ftp as a guest/anonymous).
• Unpack the tar file and place it in some reasonable place on your Mac, e.g. /usr/local/Eiffel_15.01.
• Write a bash script and make it executable (or do the equivalent in your .profile)

#For Eiffel_15.01
export ISE_EIFFEL=/usr/local/Eiffel_15.01
export ISE_PLATFORM=macosx-x86-64
export PATH=$PATH:$ISE_EIFFEL/studio/spec/$ISE_PLATFORM/bin
/usr/local/Eiffel_15.01/studio/spec/macosx-x86-64/bin/estudio $1

Be sure to disable catcall warnings in the debugger/console at the menu Executions → Execution Handling.