14 lines
254 B
Ruby
14 lines
254 B
Ruby
# frozen_string_literal: true
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class LessonError < Exception
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end
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class Lesson < ActiveRecord::Base
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has_and_belongs_to_many :students
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before_destroy :ensure_no_students
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def ensure_no_students
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raise LessonError unless students.empty?
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end
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end
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