How can I get “this->” by inputting “this.”?

Question

I want to input this. and get this-> in c++-mode.

I tried abbrev-mode and yasnippet, but failed.

In abbrev-mode, I defined an abbrev this to get this using . as a trigger key, but soon as I typed this. I got this->..

In yasnippet, I defined a snippet

# -*- mode: snippet -*-
# name: this
# key: this
# binding: .
# condition: (eq 0 (string-match "this" (buffer-substring (- (point) 4) (point))))
# --
this->

but got thisthis-> after input this..

If I remove the this in the last line of the snippet

# -*- mode: snippet -*-
# name: this
# key: this
# binding: .
# condition: (eq 0 (string-match "this" (buffer-substring (- (point) 4) (point))))
# --
->

everything seems fine but why we don't need this here ? Also, under this situation, the expansion broke the completion of company-irony even I've added yas-expand to irony-completion-trigger-commands.

What is the simplest way to achieve this ? Thanks !

Answer 1

From abbrev doc (emphasis mine):

A defined “abbrev” is a word which “expands”, if you insert it, into some different text.

this. is not a word, at least in c++-mode so this can't work.

My suggestion is to rebind in c++-mode the . key to a command testing if the current word is this, and inserting -> if so, . otherwise.

As pointed by @npostavs it's better to call self-insert-command in the second case, rather than simply calling (insert ".") as this ensures the processing is exactly what it was before we changed the binding. For example a prefix argument, if any, is handled as expected.

(defun this-dot-replace ()
  (interactive)
  (if (string= (thing-at-point 'word) "this")
      (insert "->")
    (call-interactively 'self-insert-command)))

(add-hook 'c++-mode-hook
  (lambda () (define-key c++-mode-map "." 'this-dot-replace)))

I make no guarantee this (pun intended?) is the simplest possible way.