I am a beginner making a code with module. Employee module has a struct and a function. Employees have names, id’s, salaries and jobs. I have gotten updating jobs and salaries to work.
I still need for the employee id to update for each new employee. I also want to be able to assign a first and last name for each new employee. I tried to do that following this: Learn With Me: Elixir - Structs (#18) (‘Packaging Struct Data and Functions’). But for some reason, it didn’t work, even if I copied their code.
Is this possible? Thank you in advance.
defmodule Employee do
defstruct firstName: "", lastName: "", id: 0, salary: 0, job: :none
def new() do
%Employee{}
end
def promote(employee) do
case employee.job do
:none -> employee = %{employee | job: :coder, salary: 2000}
:coder -> employee = %{employee | job: :designer, salary: 4000}
:designer -> employee = %{employee | job: :manager, salary: 6000}
:manager -> employee = %{employee | job: :ceo, salary: 8000}
end
end
def increment_id(employee) do
%Employee{employee | id: employee.id + 1}
end
end
employee = Employee.new("John", "Smith")
IO.puts("Employee name: #{employee.firstName} #{employee.lastName}. ID: #{employee.id}.
Job and salary: #{employee.job}, #{employee.salary}")
employee = Employee.promote(employee)
IO.puts("Employee name: #{employee.firstName} #{employee.lastName}. ID: #{employee.id}.
Job and salary: #{employee.job}, #{employee.salary}")
employee = Employee.promote(employee)
IO.puts("Employee name: #{employee.firstName} #{employee.lastName}. ID: #{employee.id}.
Job and salary: #{employee.job}, #{employee.salary}")
employee = Employee.demote(employee)
IO.puts("Employee name: #{employee.firstName} #{employee.lastName}. ID: #{employee.id}.
Job and salary: #{employee.job}, #{employee.salary}")
employee2 = Employee.new("Jane", "Doe")
IO.puts("Employee name: #{employee2.firstName} #{employee2.lastName}. ID: #{employee2.id}.
Job and salary: #{employee2.job}, #{employee2.salary}")
This line we call the function new/2 in a module called Employee. In your case this function doesn’t exist. You defined the function new/0 that doesn’t take any parameter.
So let’s update our code to have the right function:
defmodule Employee do
defstruct first_name: "", last_name: "", id: 0, salary: 0, job: :none
# Obviously you can call parameter without _var
# I just add it to clarify the code in the function
def new(first_name_var, last_name_var) do
%Employee{first_name: first_name_var, last_name: last_name_var}
end
def promote(employee) do
# ...
end
def increment_id(employee) do
# ...
end
end
in Elixir only modules names are in camel case, otherwise it’s in kebab case that’s why I changed firstName to first_name.
If you have any other question just ask
Have a great day
edit : Try to create a function display/1 that take an employee as parameter. Then simply call Employee.display(employee) to execute the IO.puts/1
The main objectives of Modules is to reduce the code size meaning when you can factor something, create a function.
Thank you, I didn’t know about the camel/kebab case. How would you go about incrementing the id for each created employee? Is it even possible with Elixir?
Yeah, you can use Agent or GenServer to hold the value.
Or simply use the previous employee’s id and increment it by one.
employee1 = Employee.new("John", "Doe")
employee2 = Employee.new("Jane", "Doe")
# So here employee1.id == 0 and employee2.id == 0
employee2 = %{employee2 | id: employee1.id + 1}
Often this will be enough
Or using an GenServer
defmodule MyGenServer do
use GenServer
def start_link(state) do
GenServer.start_link(MyGenServer, state, name: :my_gen_server)
end
# Here state is the 2nd param of `GenServer.start_link/3`
def init(state), do: {:ok, state}
def incr do
# Here we use the name of the GenServer
GenServer.call(:my_gen_server, :incr)
end
# server side, access through GenServer.call or GenServer.cast
def handle_call(:incr, _from, state) do
{:reply, state, state + 1}
end
end
# code to use the GenServer that will manage our id incr
MyGenServer.start_link(0) # {:ok, pid} =>
# We dont really care of the pid here because we named our GenServer
# A named GenServer is accessible using its name instead of its PID
MyGenServer.inc() # 0
MyGenServer.inc() # 1
MyGenServer.inc() # 2
MyGenServer.inc() # 3
So update your Employee module to have
defmodule Employee do
defstruct first_name: "", last_name: "", id: nil, salary: 0, job: :none
# Obviously you can call parameter without _var
# I just add it to clarify the code in the function
def new(first_name_var, last_name_var) do
%Employee{
first_name: first_name_var,
last_name: last_name_var,
id: MyGenServer.inc()
}
end
