Call function only when the plugin is loaded

Question

I use Plug as my plugin manager and have this line:

Plug 'MyPlugin', { 'for' : 'c'}

which means it should only load the plugin MyPlugin when a file of the filetype c is opened.

This works fine, but right after that I have a function call: call MyPlugin#doSomething(...) which leads to an error everytime I dont open a file of the filetype c. is there some kind of if statement to check if the plugin MyPlugin has been loaded?

Answer 1

Rather than have my ~/.vimrc load a plugin ahead of when it would normally be loaded, I usually solve this problem in one of two ways.

1. Call the function in a ~/.vimrc/after/plugin/MyPlugin.vim file.

   if exists('*MyPlugin#doSomething') call MyPlugin#doSomething(args) endif

2. Call the function in an autocommand in your ~/.vimrc so that it will be executed after plugins are loaded.

   au VimEnter * if exists('*MyPlugin#doSomething') | call MyPlugin#doSomething(args) | endif
   

Answer 2

In the case of autoload functions, what I usually do is the following

1. I check whether the function is known
2. If not I explicitly try-to-source its autoload plugin, with :runtime that takes care of &rtp, and that fails silently.
3. I check again whether the function is known

IOW:

if ! exists('*MyPlugin#doSomething')
   runtime autoload/MyPlugin.vim
endif
if exists('*MyPlugin#doSomething')
    call MyPlugin#doSomething(args)
endif

Note: that if your plugin is mainly made of ftplugin and of autoloaded scripts, I don't see the point of the { 'for' : 'c'} specification.

Answer 3

Almost all the proposed solutions try to execute or not execute the code if the plugin is loaded or not. But I think that what you want is to execute some action when the plugin gets loaded. So it is not a matter of not executing the code, but executing it at the right moment. According to Plug documentation, when the plugin is loaded an User event with the name of the plugin is triggered, then you can use that event in autocmd commands. For example, in my case I want to execute the register function of the plugin called vim-wich-key. My Vimrc is split into several files, but I will put everything togheter in this example:

Plug 'liuchengxu/vim-which-key', { 'on': ['WhichKey', 'WhichKey!'] }

autocmd! User vim-which-key call which_key#register('<Space>', "g:which_key_map")

As you can see, the plugin is loaded on the first call to one of it's functions and my register call only happens when the plugin gets loaded. I verified that this works perfectly.