Bash assign variable result of bool function, then check

I am trying to create a function which returns 0 or 1 (i.e. true or false) and takes an argument, then create a variable in another which stores the results of that function. Finally check if that variable is 0 or 1 (true or false)

Here is a sample of what I am attempting

#!/bin/bash

_has_string() {
  if [ $1 == "string" ];
    return 0
  else
    return 1
  fi
}

_my_func() {
  var=$(_has_string "string")
  if [ $var == "0" ]; then
    echo "var contains string"
  else
    echo "var does not contain string"
  fi
}

_my_func

I have tried a few variations of this and can not seem to find a way to get it to work. All of my variations basically just return the $var as nothing. Not a 0. Not null. Literally it is just blank.