How to copy and paste arguments into function parenthesis?

Question

I constantly need to copy existing variable names or expressions as arguments for my current typing function:

// int TyrionLannister;

int JonSnow;

...

int AryaStark;

...

// int DaenerysTargaryen;

foo();
   ^ current currsor

I want to change foo() to:

foo(JonSnow, AryaStark, TyrionLannister, DaenerysTargaryen)

I have used two methods to do the job so far:

1. use autocomplete plugin such as ycm, i can type "js", and select "JonSnow" from popup list.

2. sometimes plugin can't help me, because target variable is commented or it's some compound expression or whatever reason, i have to copy and paste by myself.
   

   I have to move my cursor to the variable if i want to copy it, sometimes i use G, sometimes i use HML and a lot of {,} and j k, some times even/ seemes to be a good choice.

   Sometimes i copy all variables into different registers abc..., then ` . or gi to go back to foo(), paste from a, add comma, paste from b, add comma, etc. Sometimes i copy only one variable, go back to foo(), add comma, paste it, then repeat the process for other variables.

Method 2 is quite awkward, i hate it so much that sometimes i type the arguments manually(i know i shouldn't do it manually).

How should i change my workflow? What's your workflow for this problem?

Answer 1

As @D. Ben Knoble mentioned, I'd use <C-n> and <C-p> which will look mostly (but not only, cf :help i_ctrl-n for more information) in the words in the opened files, making the completion quite "local", and appropriate in your case.

Regarding the completion of Vim, I'd encourage you to have a look at it, my favourite ones being the path completion (:help i_CTRL-X_CTRL-F) and the whole line completion (i_CTRL-X_CTRL-L). But the tag completion is definitely worth having a look. Take them and get comfortable with them one after the other, and it will be less daunting.