Remove homebrew cocoapods installation in catalina, and install directly from gem, zsh version

fix_cocoapods_catalina.sh

#! /bin/zsh

install_cocoapods () {
    echo "Installing cocoapods with gem"
    # Creating new gems home if it doesnt't exist
    if [ ! -d "$HOME/.gem" ]; then
        mkdir "$HOME/.gem"
    fi

    # Adding to current session
    export GEM_HOME="$HOME/.gem"
    export PATH="$GEM_HOME/bin:$PATH"

    # Adding for future sessions
    if test -f "$HOME/.zshrc"; then
        echo 'Adding $GEM_HOME env var and then adding it to your $PATH'
        echo '' >> "$HOME/.zshrc"
        echo 'export GEM_HOME="$HOME/.gem"' >> "$HOME/.zshrc"
        echo 'export PATH="$GEM_HOME/bin:$PATH"' >> "$HOME/.zshrc"
    fi

    # Installing cocoapods
    gem install cocoapods
    which pod
    pod --version
}

uninstall_cocoapods_homebrew () {
    which -s brew
    if [[ $? != 0 ]] ; then
        echo "Homebrew not installed, skipping uninstalling cocoapods from homebrew"
    else
        brew uninstall cocoapods
    fi
}

if ! type "pod" > /dev/null; then
    echo "You don't have cocoapods installed..."    
else
    echo "Trying to uninstall it from homebrew first"
    uninstall_cocoapods_homebrew    
fi

install_cocoapods

Trying to uninstall it from homebrew first
/usr/local/bin/brew -> /usr/local/Homebrew/bin/brew
Uninstalling /usr/local/Cellar/cocoapods/1.10.1... (13,132 files, 30.4MB)
Installing cocoapods with gem
Adding $GEM_HOME env var and then adding it to your $PATH
Fetching ffi-1.14.2.gem
Fetching ethon-0.12.0.gem
Fetching typhoeus-1.4.0.gem
Fetching netrc-0.11.0.gem
Fetching cocoapods-core-1.10.1.gem
Fetching public_suffix-4.0.6.gem
Fetching addressable-2.7.0.gem
Fetching claide-1.0.3.gem
Fetching cocoapods-deintegrate-1.0.4.gem
Fetching cocoapods-downloader-1.4.0.gem
Fetching cocoapods-plugins-1.0.0.gem
Fetching cocoapods-search-1.0.0.gem
Fetching cocoapods-trunk-1.5.0.gem
Fetching cocoapods-try-1.2.0.gem
Fetching molinillo-0.6.6.gem
Fetching atomos-0.1.3.gem
Fetching cocoapods-1.10.1.gem
Fetching colored2-3.1.2.gem
Fetching nanaimo-0.3.0.gem
Fetching xcodeproj-1.19.0.gem
Fetching escape-0.0.4.gem
Fetching fourflusher-2.3.1.gem
Fetching gh_inspector-1.1.3.gem
Fetching ruby-macho-1.4.0.gem
Building native extensions. This could take a while...
ERROR:  Error installing cocoapods:
	ERROR: Failed to build gem native extension.

    current directory: /Users/feiya200/.gem/gems/ffi-1.14.2/ext/ffi_c
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby -I /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0 -r ./siteconf20210304-70399-l2ualq.rb extconf.rb
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
	--with-opt-dir
	--without-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/$(RUBY_BASE_NAME)
	--with-ffi_c-dir
	--without-ffi_c-dir
	--with-ffi_c-include
	--without-ffi_c-include=${ffi_c-dir}/include
	--with-ffi_c-lib
	--without-ffi_c-lib=${ffi_c-dir}/lib
	--enable-system-libffi
	--disable-system-libffi
	--with-libffi-config
	--without-libffi-config
	--with-pkg-config
	--without-pkg-config
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:467:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:546:in `block in try_link0'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/tmpdir.rb:93:in `mktmpdir'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:543:in `try_link0'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:570:in `try_link'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:672:in `try_ldflags'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/mkmf.rb:1832:in `pkg_config'
	from extconf.rb:9:in `system_libffi_usable?'
	from extconf.rb:42:in `<main>'

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /Users/feiya200/.gem/extensions/universal-darwin-19/2.6.0/ffi-1.14.2/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /Users/feiya200/.gem/gems/ffi-1.14.2 for inspection.
Results logged to /Users/feiya200/.gem/extensions/universal-darwin-19/2.6.0/ffi-1.14.2/gem_make.out
pod not found
install_cocoapods:22: command not found: pod

how to use it?

it worked for me, thanks!