132 lines
4.4 KiB
Plaintext
132 lines
4.4 KiB
Plaintext
*usr_50.txt* For Vim version 9.1. Last change: 2022 Jun 20
|
|
|
|
VIM USER MANUAL - by Bram Moolenaar
|
|
|
|
Advanced Vim script writing
|
|
|
|
|
|
|50.1| Exceptions
|
|
|50.2| Function with variable number of arguments
|
|
|50.3| Restoring the view
|
|
|
|
Next chapter: |usr_51.txt| Create a plugin
|
|
Previous chapter: |usr_45.txt| Select your language (local)
|
|
Table of contents: |usr_toc.txt|
|
|
|
|
==============================================================================
|
|
*50.1* Exceptions
|
|
|
|
Let's start with an example: >
|
|
|
|
try
|
|
read ~/templates/pascal.tmpl
|
|
catch /E484:/
|
|
echo "Sorry, the Pascal template file cannot be found."
|
|
endtry
|
|
|
|
The `read` command will fail if the file does not exist. Instead of
|
|
generating an error message, this code catches the error and gives the user a
|
|
message with more information.
|
|
|
|
For the commands in between `try` and `endtry` errors are turned into
|
|
exceptions. An exception is a string. In the case of an error the string
|
|
contains the error message. And every error message has a number. In this
|
|
case, the error we catch contains "E484:". This number is guaranteed to stay
|
|
the same (the text may change, e.g., it may be translated).
|
|
|
|
Besides being able to give a nice error message, Vim will also continue
|
|
executing commands after the `:endtry`. Otherwise, once an uncaught error is
|
|
encountered, execution of the script/function/mapping will be aborted.
|
|
|
|
When the `read` command causes another error, the pattern "E484:" will not
|
|
match in it. Thus this exception will not be caught and result in the usual
|
|
error message and execution is aborted.
|
|
|
|
You might be tempted to do this: >
|
|
|
|
try
|
|
read ~/templates/pascal.tmpl
|
|
catch
|
|
echo "Sorry, the Pascal template file cannot be found."
|
|
endtry
|
|
|
|
This means all errors are caught. But then you will not see an error that
|
|
would indicate a completely different problem, such as "E21: Cannot make
|
|
changes, 'modifiable' is off". Think twice before you catch any error!
|
|
|
|
Another useful mechanism is the `finally` command: >
|
|
|
|
var tmp = tempname()
|
|
try
|
|
exe ":.,$write " .. tmp
|
|
exe "!filter " .. tmp
|
|
:.,$delete
|
|
exe ":$read " .. tmp
|
|
finally
|
|
delete(tmp)
|
|
endtry
|
|
|
|
This filters the lines from the cursor until the end of the file through the
|
|
"filter" command, which takes a file name argument. No matter if the
|
|
filtering works, if something goes wrong in between `try` and `finally` or the
|
|
user cancels the filtering by pressing CTRL-C, the `delete(tmp)` call is
|
|
always executed. This makes sure you don't leave the temporary file behind.
|
|
|
|
The `finally` does not catch the exception, the error will still abort
|
|
further execution.
|
|
|
|
More information about exception handling can be found in the reference
|
|
manual: |exception-handling|.
|
|
|
|
==============================================================================
|
|
*50.2* Function with variable number of arguments
|
|
|
|
Vim enables you to define functions that have a variable number of arguments.
|
|
The following command, for instance, defines a function that must have 1
|
|
argument (start) and can have up to 20 additional arguments: >
|
|
|
|
def Show(start: string, ...items: list<string>)
|
|
|
|
The variable "items" will be a list in the function containing the extra
|
|
arguments. You can use it like any list, for example: >
|
|
|
|
def Show(start: string, ...items: list<string>)
|
|
echohl Title
|
|
echo "start is " .. start
|
|
echohl None
|
|
for index in range(len(items))
|
|
echon $" Arg {index} is {items[index]}"
|
|
endfor
|
|
echo
|
|
enddef
|
|
|
|
You can call it like this: >
|
|
|
|
Show('Title', 'one', 'two', 'three')
|
|
< start is Title Arg 0 is one Arg 1 is two Arg 2 is three ~
|
|
|
|
This uses the `echohl` command to specify the highlighting used for the
|
|
following `echo` command. `echohl None` stops it again. The `echon` command
|
|
works like `echo`, but doesn't output a line break.
|
|
|
|
If you call it with one argument the "items" list will be empty.
|
|
`range(len(items))` returns a list with the indexes, what `for` loops over,
|
|
we'll explain that further down.
|
|
|
|
==============================================================================
|
|
*50.3* Restoring the view
|
|
|
|
Sometimes you want to jump around, make a change and then go back to the same
|
|
position and view. For example to change something in the file header. This
|
|
can be done with two functions: >
|
|
|
|
var view = winsaveview()
|
|
# Move around, make changes
|
|
winrestview(view)
|
|
|
|
==============================================================================
|
|
|
|
Next chapter: |usr_51.txt| Create a plugin
|
|
|
|
Copyright: see |manual-copyright| vim:tw=78:ts=8:noet:ft=help:norl:
|