vim tip: select all lines matching pattern·wheelibin.co.uk

Background

Various IDEs/tools I have used over the years have provided a code action Extract Interface, which would take the function signatures of a class and produce an interface from them.

I found myself needing to do this in Neovim and went looking for a solution.

A vim way?

Essentially Extract Interface boils down to “Copy all function signatures to a new code block”.

To get us most of the way there then we can further simplify this to Copy all lines matching a pattern.

It turns out this is very simple in vim/neovim:

Copy

" clear register a
qaq
" yank all lines matching patten into register a
:g/pattern/y A

Paste:

"ap

An example using go

func (h *HueAPIService) GetRooms() ([]models.HughGroup, error) {
    ...
}

func (h *HueAPIService) GetZones() ([]models.HughGroup, error) {
    ...
}

func (h *HueAPIService) GetAllGroups() ([]models.HughGroup, error) {
    ...
}

First we clear the register we are using

qaq

Then we copy the function signature lines

:g/func (h \*Hue/y A

Then we can paste these lines into an empty interface declaration

type SomeInterface interface {
  // cursor here
}

Paste from register a

"ap

We then have something like this.

type SomeInterface interface {
    func (h *HueAPIService) GetRooms() ([]models.HughGroup, error) {
    func (h *HueAPIService) GetZones() ([]models.HughGroup, error) {
    func (h *HueAPIService) GetAllGroups() ([]models.HughGroup, error) {
}

All that’s left to do is remove some extra things from the lines, but simple find/replace can easily take care of that.

yes, just blindly creating an interface from something is usually not the way to work in go, this is purely an example

vim tip: select all lines matching pattern