Why are class methods useful? Are they good practice?

Here's a spec for a local method :

 describe '#description' do
    it 'describes what task is being done' do
      test_task = Task.new("wash the dishes")
      test_task2 = Task.new("feed the dog")
      expect(test_task.description).to eq "wash the dishes"
    end
end

I am calling the description method on a string so that I can get just this string back, or some other strings that I put inside it. I called for test_task back instead of test task 2.

CLASS method

 describe '.all' do
   it 'empty at first' do
     expect(Task.all).to eq []
   end
end

I am calling the all method on the entire class, so that I can get a list (array) back of all the tasks that I added to the array. Right now it is empty, so I have to add a "local" save method below.

 describe '#save' do
    it 'adds task and saves to the list' do
      test_task = Task.new("go to the grocer")
      test_task2 = Task.new("cook dinner for kids")
      test_task.save
      test_task2.save
      expect(Task.all).to eq [test_task, test_task2]
    end
end

So now that class method gave me back all the things I added within it instead of one thing like "description." The class method would be able to take everything within itself and do something.

When you want the class method to have access to everything within it, then it makes sense. It just depends on what the method is. In general, it wont be doing too much work. What if "save" was a class method? Somehow I think it would just change and overwrite everything to whatever you put in, rather than add multiple things to the list

Other methods to keep in mind are .clear and .find.

The find or search method would look through all of the things you add in your program and give back a specific one.

I don't know if this helps. Sorry :)