如何在rails上使ruby处理来自MySQL的重复记录错误

class User< ApplicationRecord
  validates_uniqueness_of :username
end

def create_user
  user = User.new(username: params[:username], password: params[:password])
  begin
    user.save!
    flash[:notice] = "User created successfully"
  rescue ActiveRecord::RecordInvalid => e
    if e.message.include?("username has already been taken")
      flash[:error] = "Username already exists"
    else
      flash[:error] = "Error creating user: #{e.message}"
    end
  end
end

def create_user
  user = User.where(username: params[:username]).first_or_create(password: params[:password])
  if user.new_record?
    flash[:notice] = "User created successfully"
  else
    flash[:error] = "Username already exists"
  end
end

def get_unique_usernames
  usernames = User.pluck(:username).uniq
end