はじめに
デバッグについて調べていた際にpryのことをついて勉強。
binding.pryくらいしか使ってこなかったデバッグツールについて簡単にまとめておきます。
pryって？
Rubyには標準ではirb(Interactive Ruby)が装備されていますが、
それをより便利にしたものになります。
初学者の方もirbを起動させてrubyのコードを打ったことがあるのではないでしょうか？
Railsではデバッグ（バグなどを発見すること）をする際に使われます。
pryを使うにはGemfileにgemを追加する必要があります。
有名なものでpry-railsとpry-byebugがあります。
今回はpry-railsで説明します。
Gemfile
gem 'pry-rails'
Gemfileに追加して
% bundle install
bundle installしましょう。
これで使えるようになります。
pryを使うことのメリット
- 便利なコマンドが標準装備されている
- shellコマンドが使用可能
便利なコマンドが標準装備
よく使われるのはbinding.pryだと思います。
binding.pryとは
投稿フォームに入力した情報がデータベースに保存されないというエラーが発生したとします。
そういった場合、原因がどのコードにあるのかをbinding.pryという文字列をコントローラーなどのコード内に記述するとそこがブレイクポイントとなりrailsの処理を止めることができます。
その場所でpryが記述して変数の中身やパラメーターなどの確認をすることができます。
便利なコマンド一例
pryでは他に便利な機能が用意されていて
helpと打つとコマンドの一覧が表示されます。
[7] pry(main)> help
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
find-method Recursively search for a method within a class/module or the current namespace.
ls Show the list of vars and methods in the current scope.
pry-backtrace Show the backtrace for the pry session.
raise-up Raise an exception out of the current pry instance.
reset Reset the repl to a clean state.
watch Watch the value of an expression and print a notification whenever it changes.
whereami Show code surrounding the current context.
:...skipping...
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
find-method Recursively search for a method within a class/module or the current namespace.
ls Show the list of vars and methods in the current scope.
pry-backtrace Show the backtrace for the pry session.
raise-up Raise an exception out of the current pry instance.
reset Reset the repl to a clean state.
watch Watch the value of an expression and print a notification whenever it changes.
whereami Show code surrounding the current context.
wtf? Show the backtrace of the most recent exception.
Editing
! Clear the input buffer.
amend-line Amend a line of input in multi-line mode.
edit Invoke the default editor on a file.
hist Show and replay readline history.
play Playback a string variable, method, line, or file as input.
show-input Show the contents of the input buffer for the current multi-line expression.
Introspection
ri View ri documentation.
show-doc Show the documentation for a method or class.
show-source Show the source for a method or class.
:...skipping...
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
find-method Recursively search for a method within a class/module or the current namespace.
ls Show the list of vars and methods in the current scope.
pry-backtrace Show the backtrace for the pry session.
raise-up Raise an exception out of the current pry instance.
reset Reset the repl to a clean state.
watch Watch the value of an expression and print a notification whenever it changes.
whereami Show code surrounding the current context.
wtf? Show the backtrace of the most recent exception.
Editing
! Clear the input buffer.
amend-line Amend a line of input in multi-line mode.
edit Invoke the default editor on a file.
hist Show and replay readline history.
play Playback a string variable, method, line, or file as input.
show-input Show the contents of the input buffer for the current multi-line expression.
Introspection
ri View ri documentation.
show-doc Show the documentation for a method or class.
show-source Show the source for a method or class.
stat View method information and set _file_ and _dir_ locals.
Commands
import-set Import a pry command set.
:...skipping...
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
find-method Recursively search for a method within a class/module or the current namespace.
ls Show the list of vars and methods in the current scope.
pry-backtrace Show the backtrace for the pry session.
raise-up Raise an exception out of the current pry instance.
reset Reset the repl to a clean state.
watch Watch the value of an expression and print a notification whenever it changes.
whereami Show code surrounding the current context.
wtf? Show the backtrace of the most recent exception.
Editing
! Clear the input buffer.
amend-line Amend a line of input in multi-line mode.
edit Invoke the default editor on a file.
hist Show and replay readline history.
play Playback a string variable, method, line, or file as input.
show-input Show the contents of the input buffer for the current multi-line expression.
Introspection
ri View ri documentation.
show-doc Show the documentation for a method or class.
show-source Show the source for a method or class.
stat View method information and set _file_ and _dir_ locals.
Commands
import-set Import a pry command set.
Aliases
!!! Alias for `exit-program`
!!@ Alias for `exit-all`
$ Alias for `show-source`
/whereami[!?]+/ Alias for `whereami`
:...skipping...
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
find-method Recursively search for a method within a class/module or the current namespace.
ls Show the list of vars and methods in the current scope.
pry-backtrace Show the backtrace for the pry session.
raise-up Raise an exception out of the current pry instance.
reset Reset the repl to a clean state.
watch Watch the value of an expression and print a notification whenever it changes.
whereami Show code surrounding the current context.
wtf? Show the backtrace of the most recent exception.
Editing
! Clear the input buffer.
amend-line Amend a line of input in multi-line mode.
edit Invoke the default editor on a file.
hist Show and replay readline history.
play Playback a string variable, method, line, or file as input.
show-input Show the contents of the input buffer for the current multi-line expression.
Introspection
ri View ri documentation.
show-doc Show the documentation for a method or class.
show-source Show the source for a method or class.
stat View method information and set _file_ and _dir_ locals.
Commands
import-set Import a pry command set.
Aliases
!!! Alias for `exit-program`
!!@ Alias for `exit-all`
$ Alias for `show-source`
/whereami[!?]+/ Alias for `whereami`
? Alias for `show-source -d`
@ Alias for `whereami`
file-mode Alias for `shell-mode`
find-routes Alias for `find-route`
:...skipping...
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
Help
help Show a list of commands or information about a specific command.
Context
cd Move into a new context (object or scope).
find-method Recursively search for a method within a class/module or the current namespace.
ls Show the list of vars and methods in the current scope.
pry-backtrace Show the backtrace for the pry session.
raise-up Raise an exception out of the current pry instance.
reset Reset the repl to a clean state.
watch Watch the value of an expression and print a notification whenever it changes.
whereami Show code surrounding the current context.
wtf? Show the backtrace of the most recent exception.
Editing
! Clear the input buffer.
amend-line Amend a line of input in multi-line mode.
edit Invoke the default editor on a file.
hist Show and replay readline history.
play Playback a string variable, method, line, or file as input.
show-input Show the contents of the input buffer for the current multi-line expression.
Introspection
ri View ri documentation.
show-doc Show the documentation for a method or class.
show-source Show the source for a method or class.
stat View method information and set _file_ and _dir_ locals.
Commands
import-set Import a pry command set.
Aliases
!!! Alias for `exit-program`
!!@ Alias for `exit-all`
$ Alias for `show-source`
/whereami[!?]+/ Alias for `whereami`
? Alias for `show-source -d`
@ Alias for `whereami`
file-mode Alias for `shell-mode`
find-routes Alias for `find-route`
history Alias for `hist`
quit Alias for `exit`
quit-program Alias for `exit-program`
reload-method Alias for `reload-code`
show-method Alias for `show-source`
Input and output
.<shell command> All text following a '.' is forwarded to the shell.
cat Show code from a file, pry's input buffer, or the last exception.
change-inspector Change the current inspector proc.
change-prompt Change the current prompt.
clear-screen Clear the contents of the screen/window pry is running in.
fix-indent Correct the indentation for contents of the input buffer
list-inspectors List the inspector procs available for use.
save-file Export to a file using content from the repl.
shell-mode Toggle shell mode. bring in pwd prompt and file completion.
Misc
pry-version Show pry version.
reload-code Reload the source file that contains the specified code object.
toggle-color Toggle syntax highlighting.
Navigating pry
!pry Start a pry session on current self.
disable-pry Stops all future calls to pry and exits the current session.
exit Pop the previous binding.
exit-all End the current pry session.
exit-program End the current program.
jump-to Jump to a binding further up the stack.
nesting Show nesting information.
switch-to Start a new subsession on a binding in the current stack.
Rails
find-route See which urls match a given controller.
recognize-path See which route matches a url.
show-middleware Show all middleware (that rails knows about).
show-model Show the given model.
show-models Show all models.
show-routes Show all routes in match order.
(END)
たくさんあります。
show-routes
例えばshow-routesというコマンドはルーティングを確認することができます。
ルーティングの確認だとrails routesがあるじゃんと思うかと思いますが
show-routesはより高速に表示されます。
show-models
`show-models｀というコマンドはアプリケーションにある全てのモデル、カラム、データタイプを返してくれるコマンドです。
pryでshellコマンドを使う
pryでshellコマンドをコンソール上で入力するには.をつけて実行しないとエラーになります。
終わりに
なんとなく使っていたものもいろいろ便利な機能があるのだと思いました。
深掘りって大事ですね。
日々更新していきます。
参考サイト
Pikawaka 【Rails】Pryについて徹底解説！
TechTechMedia 【Rails】Rails開発者に絶対おすすめしたいデバッグ手法５選（初心者向け）