Calling a function with a variable in vim

Question

This seems like it should be the easiest thing to do, but I'm having trouble calling a vim function with a variable. For example, I have the following function:

func Run1()
    echom 'Running run1'
endfunc

This works fine:

:call Run1()
" Running run1

Now, to add a function parameter:

func Run2(var)
    echom 'Running run2 with var ' . var
endfunc

And calling it should be as simple as:

:call Run2('hello')
# E121: Undefined variable: var

But I get an error. How should I function be called then?

Answer 1

It’s the usage that’s wrong: all function-arguments must be prefixed with a: in the body of the function (but NOT in the function declaration line).

This is because the default is one of l:/s:/g:, so the argument doesn’t even get seen (it’s in a different dictionary).