Loading and compiling modules

In this recipe, we will be importing two files that define the Greeter and Echoer modules into our IEx session.

In the following lines, we will list the contents of these modules:

code\greeter.ex
defmodule Greeter do

  def greet(name \\ "you") do
    "Hello #{name} !"
  end

end

code/echoer.ex
defmodule Echoer do

  def echo(msg) do
    IO.puts "#{msg} ... #{msg} ...... #{msg}"
  end

end

We will follow these steps to load and compile the modules:

When c("file_name.ex") is invoked from IEx, the file is loaded and compiled (a corresponding file with the .beam extension will be created).

The module (or modules) defined on each imported file become available. It is possible to invoke functions on these modules using the ModuleName.function_name(args) syntax.

If a module_name.beam file exists for a given module, then every time you import that module into an IEx session, you will see the following warning:

module_name.ex:1: warning: redefining module ModuleName

The warning means that a new compiled .beam file is being created, potentially redefining the module. If no changes were made to the source code, the code will be the same, although the warning is still issued.

In step 6, the pipe operator (|>) is used to simplify the code. This operator means that the output of the left operation will be fed as the first argument to the right operation.

This is equivalent to writing the following:

Echoer.echo(Greeter.greet("Me"))

In steps 2 and 3, the greeter.ex and echoer.ex files are imported without indicating the path because they are under the same directory from where the IEx session was started.

It is possible to use relative or full paths when loading files: