Advanced IEx Helpers: Mastering Commands and Features in Elixir

Following our previous exploration of IEx basics, let's dive into the advanced helpers and features that make IEx an even more powerful tool for Elixir developers. These helpers can significantly improve your development workflow and code understanding.

Table of Contents

• Value Retrieval and Type Information
• Code Inspection and Documentation
• Module Management
• Process Information
• Shell Navigation and History

Value Retrieval and Type Information

The v/1 Helper

Retrieve values from previous expressions:

iex(1)> 40 + 2
42
iex(2)> v(1)  # Gets the result of line 1
42

The t/1 Helper

Display type information for modules:

iex(3)> t Map
@type key() :: any()

@type value() :: any()

Code Inspection and Documentation

The b/1 Helper

List all callbacks for a module:

iex(4)> b GenServer
@callback init(init_arg :: term()) ::
            {:ok, state}
            | {:ok, state, timeout() | :hibernate | {:continue, continue_arg :: term()}}
            | :ignore
            | {:stop, reason :: any()}
          when state: any()
# ... more callbacks ...

The h/1 Helper with Arity

Get detailed documentation for specific functions:

iex(5)> h Enum.map/2
                            def map(enumerable, fun)

  @spec map(t(), (element() -> any())) :: list()

Returns a list where each element is the result of invoking fun on each
corresponding element of enumerable.
# ... rest of the documentation ...

Module Management

The l/1 Helper

Reload a module during development:

iex(6)> l Map
{:module, Map}

The exports/1 Helper

List all exported functions in a module:

iex(7)> exports(String)
at/2                     bag_distance/2           byte_slice/3
capitalize/1             capitalize/2             chunk/2
# ... more exports ...

Process Information

The i/1 Helper

Get detailed information about any term:

iex(8)> pid = spawn(fn -> :ok end)
#PID<0.107.0>
iex(9)> i(pid)
Term
  #PID<0.107.0>
Data type
  PID
Alive
  false
Description
  Use Process.info/1 to get more info about this process
Reference modules
  Process, Node
Implemented protocols
  IEx.Info, Inspect

Process Creation and Reference

Create PIDs and interact with the current node:

iex(10)> pid(0, 100, 0)
#PID<0.100.0>
iex(11)> node()
:nonode@nohost

Value Inspection

The inspect/2 Helper

Customize how values are displayed:

iex(12)> inspect([1, 2, 3], limit: 2)
"[1, 2, ...]"

Memory Information

Get detailed memory usage information:

iex(13)> :erlang.memory()
[
  total: 43662208,
  processes: 18319664,
  processes_used: 18319520,
  system: 25342544,
  atom: 491713,
  atom_used: 470964,
  binary: 988992,
  code: 10158566,
  ets: 598000
]

Shell Navigation and History

Command History

• Use up and down arrow keys to navigate through previous commands
• Use Ctrl+R to perform reverse search through command history
• Use Ctrl+G to enter the user switch command interface

Shell Management

• Use Ctrl+C twice to exit IEx
• Use Ctrl+C once followed by "a" to abort
• Use clear() to clear the screen

Best Practices

1. Use inspect/2 with different options to better understand complex data structures
2. Leverage v/1 to reference previous results in calculations
3. Use i/1 to get detailed information about any term
4. Make use of exports/1 to discover available functions in modules
5. Keep your modules reloaded with l/1 during development

Conclusion

These IEx helpers significantly enhance your ability to explore and understand Elixir code interactively. By mastering these tools, you can become more efficient in development and code analysis.

While we've covered many powerful features here, remember that IEx offers even more capabilities when it comes to debugging, production monitoring, and customization - topics we'll explore in future articles.

Next Steps

• Practice using these helpers in your daily development workflow
• Combine different helpers for more complex analysis
• Stay tuned for our upcoming articles on debugging with IEx and production usage