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Live help

kyrylo edited this page · 8 revisions

Live help system

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One of the design goals of Pry was for it to be self-documenting. To that end, Pry provides commands that yield documentation on nearly every aspect of Pry from within the REPL itself.

Viewing a Pry method's documentation

Since Pry is simply Ruby code, all documentation on its methods are available using the standard show-doc command.


pry(main)> ? Pry#valid_expression?

From: /Users/john/.rvm/gems/ruby-1.9.2-p180/gems/pry-0.9.2/lib/pry/pry_instance.rb @ line 458:
Number of lines: 7

signature: valid_expression?(code)

Determine if a string of code is a valid Ruby expression.
Ruby 1.9 uses Ripper, Ruby 1.8 uses RubyParser.
param [String] code The code to validate.
return [Boolean] Whether or not the code is a valid Ruby expression.
  valid_expression?("class Hello") #=> false
  valid_expression?("class Hello; end") #=> true

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Learning about Pry's configuration options

Live help may be particularly useful when learning about Pry's configuration options. Most of these are documented methods in the Pry.config namespace.


pry(main)> ls -m Pry.config
[:__binding_impl__, :color, :color=, :commands, :commands=, :editor, :editor=, :exception_handler, :exception_handler=, :has_pry_doc, :has_pry_doc=, :history, :history=, :hooks, :hooks=, :input, :input=, :memory_size, :memory_size=, :output, :output=, :pager, :pager=, :plugins, :plugins=, :print, :print=, :prompt, :prompt=, :result_pager, :result_pager=, :results_pager, :results_pager=, :should_load_plugins, :should_load_plugins=, :should_load_rc, :should_load_rc=]
pry(main)> ? Pry.config.editor

From: /Users/john/.rvm/gems/ruby-1.9.2-p180/gems/pry-0.9.2/lib/pry/config.rb @ line 58:
Number of lines: 12

signature: editor()

The default editor to use. Defaults to $EDITOR or nano if
$EDITOR is not defined.
If editor is a String then that string is used as the shell
command to invoke the editor. If editor is callable (e.g a
Proc) then file and line are passed in as parameters and the
return value of that callable invocation is used as the exact
shell command to invoke the editor.
example String
  Pry.editor = "emacsclient"
example Callable
  Pry.editor = proc { |file, line| "emacsclient #{file} +#{line}" }
return [String, #call]

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The help command (Pry command documentation)

Pry's commands are not methods and so cannot easily be documented in the same way as methods (using show-doc). Instead commands have their own documentation system organized around the help command.

Typing help at the prompt will retrieve a list of all available commands. If you pass a parameter to help where that parameter is the name of a command you will restrict the output to the help for just that command.

Example: Invoking help without arguments

  help               Show a list of commands or information about a specific command

  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.
  whereami           Show code surrounding the current context.
  wtf?               Show the backtrace of the most recent exception.

  !                  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 or a method or a file as input.
  show-input         Show the contents of the input buffer for the current multi-line expression.

  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.

  gem-cd             Change working directory to specified gem's directory.
  gem-install        Install a gem and refresh the gem cache.
  gem-list           List and search installed gems.
  gem-open           Opens the working directory of the gem in your editor

  import-set         Import a Pry command set.
  install-command    Install a disabled command.

  !!!                Alias for `exit-program`
  !!@                Alias for `exit-all`
  $                  Alias for `show-source`
  ?                  Alias for `show-doc`
  @                  Alias for `whereami`
  clipit             Alias for `gist --clip`
  file-mode          Alias for `shell-mode`
  history            Alias for `hist`
  jist               Alias for `gist`
  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.
  fix-indent         Correct the indentation for contents of the input buffer
  save-file          Export to a file using content from the REPL.
  shell-mode         Toggle shell mode. Bring in pwd prompt and file completion.

  gist               Playback a string variable or a method or a file as input.
  pry-version        Show Pry version.
  reload-code        Reload the source file that contains the specified code object.
  simple-prompt      Toggle the simple prompt.
  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.

Note that help only returns a short description of each command, but this is sufficient in many cases. For more complex commands the description (retrieved by help) will indicate that more documentation is available by passing the --help switch to the command itself.

Example: A simple command

pry(main)> help cd
Start a Pry session on VAR (use `cd ..` to go back and `cd /` to return to Pry top-level)

Example: A command with further documentation available

pry(main)> help show-method
Show the source for METH. Type `show-method --help` for more info. Aliases: $, show-source
pry(main)> show-method --help
Usage: show-method [OPTIONS] [METH]
Show the source for method METH. Tries instance methods first and then methods by default.
e.g: show-method hello_method


    -l, --line-numbers          Show line numbers.
    -b, --base-one              Show line numbers but start numbering at 1 (useful for `amend-line` and `play` commands).
    -M, --instance-methods      Operate on instance methods.
    -m, --methods               Operate on methods.
    -f, --flood                 Do not use a pager to view text longer than one screen.
    -c, --context               Select object context to run under.
    -h, --help                  This message.

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