zsh using a variable in a command within a function

In .zsh, in my .zshrc file I'd like to set up a function to cd to a directory I input, but using an existing variable to write the common ~/path/to/parent/directory/$input

I've been unable to find out what the correct syntax is for this particular usage. For example, I want to enter

goto mydir

and execute a cd to ~/path/to/parent/directory/mydir

But I get an error: gt:cd:3 no such file or directory ~/path/to/parent/directory/mydir even though that directory exists.

This is the variable declaration and function I am trying:

export SITESPATH="~/path/to/parent/directory"

function gt(){
  echo "your site name is $@" 
  echo "SITESPATH: " $SITESPATH "\n"
  cd $SITESPATH/$@
}

It makes no difference if I use the above, without quotes, or "cd $SITESPATH/$@" with quotes.

Solution

I don't see the point in using $@ in your function, since you expect only one argument. $1 would be sufficient.

The problem is in the tilde which is contained in your variable SITEPATH. You need to have it expanded. You can either do it by writing

export SITESPATH=~/path/to/parent/directory

when you define the variable, or inside your function by doing a

cd ${~SITESPATH)/$1

A third possibility is to turn on glob_subst in your shell:

setopt glob_subst

In this case, you can keep your current definition of $SITESPATH, and tilde-substitution will happen automatically.