Undefined method when trying to pass through id - ruby-on-rails

Question

I'm trying to pass a project ID from its show page to an employee_projects form where I can display the projects name. The error I'm getting is
undefined local variable or method `project_id' for #<EmployeeProjectsController:0xb8bdd58>.
employee_project controller:
# GET /employee_projects/new
def new
puts params[project_id]
#project = Project.find(params[:project_id])
session[:project_id] = #project.id
#employee_project = EmployeeProject.new
end
employee_projects form
Assign worker for this project <%= project.projectName%><br>
<div class="field">
<%= f.label :employee_id %><br>
<%= f.collection_select :employee_id, Employee.all, :id, :empLastName, :prompt => "Select worker" %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
Projects show
<%= button_to "Assign!", new_employee_project_path(project_id: #project.id) , class: "btn btn-primary", :method => :get %>
Does anyone have any ideas on how to fix this?

Answer 1

In your controller try changing puts params[project_id] to puts params[:project_id].
params is a Hash so you must refer to its keys with symbols, that is :project_id. project_id is just a variable that has no value assigned to it, hence the error undefined local variable or method 'project_id' for #.
UPDATE ("Couldn't find Project with 'id'=" fix)
The button in projects' show view is not sending the parameter project_id even though you are passing it to the new_employee_project_path helper (check your url string and you will see it ending at ? with no parameters). To fix it, i recommend using a regular form instead of button_to helper.
So, instead of this line:
<%= button_to "Assign!", new_employee_project_path(project_id: #project.id) , class: "btn btn-primary", :method => :get %>
Try using this form:
<form action="<%= new_employee_project_path %>" method="get">
<input type="hidden" name="project_id" value="<%= #project.id %>">
<input type="submit" value="Assign!" class="btn btn-primary">
</form>