How to Install qt4 on macOS with homebrew? - qt

Question

I need to install the qt4 C++ framework for one of my classes. I tried using the regular installer from the download archives page for both qt4.7 and qt4.8, however I get the warning:
"Installing this package may damage your system, and the installation may fail."
So I looked into installing it via homebrew and initially tried:
brew tap cartr/qt4
brew tap-pin cartr/qt4
brew install qt#4
However, that gives me this error:
Error: Calling brew tap-pin user/tap is disabled! Use fully-scoped user/tap/formula naming instead.
I looked online for a solution and was able to install it by omitting the brew tap-pin cartr/qt4 command:
brew tap cartr/qt4
brew install qt#4
I then tried to create a sample qt program in the CLion IDE and checked the version I was using, and it said I was using qt5 (from the python anaconda distribution). So my question is, can I install both qt4 and qt5 on my system simultaneously? How do I select which version to use?

Answer 1

You can install both simultaneously. You can select which to use.
When you install qt (meaning qt5) using homebrew, it produces a "Caveats" message that answers your question.
It says will need to set certain environment variables yourself.
It says that, in only those shell sessions where you set those environment variables, qt (meaning qt5) will be available.
It says, if you want qt always available, then you can simply put those settings in your dot files.
If you install qt#4 and set those same variables to point to qt#4, then qt#4 will be available instead.
You can view the same "Caveats" message again using brew info qt. Here is the whole message:
qt is keg-only, which means it was not symlinked into /usr/local,
because Qt 5 has CMake issues when linked.
If you need to have qt first in your PATH run:
echo 'export PATH="/usr/local/opt/qt/bin:$PATH"' >> ~/.zshrc
For compilers to find qt you may need to set:
export LDFLAGS="-L/usr/local/opt/qt/lib"
export CPPFLAGS="-I/usr/local/opt/qt/include"
For pkg-config to find qt you may need to set:
export PKG_CONFIG_PATH="/usr/local/opt/qt/lib/pkgconfig"
The same commands with qt#4 made qt#4 available for me:
export PATH="/usr/local/opt/qt#4/bin:$PATH"
export LDFLAGS="-L/usr/local/opt/qt#4/lib"
export CPPFLAGS="-I/usr/local/opt/qt#4/include"
export PKG_CONFIG_PATH="/usr/local/opt/qt#4/lib/pkgconfig"
By the way, I installed qt#4 using the user/tap/formula syntax: brew install cartr/qt4/qt#4