```ruby
require 'active_model/model'

class ProjectRequest

  include ActiveModel::Model
  include ActiveModel::MassAssignmentSecurity

  attr_accessor :project_uri, :nature_uri, :sender, :organisation

  # TODO validate project isn't already member of project

  validates :project_uri, :nature_uri, presence: true

  def attributes=(values)
    sanitize_for_mass_assignment(values).each do |attr, value|
      public_send("#{attr}=", value)
    end
  end

  def project
    @project ||= Project.find(self.project_uri)
  end

  # Owner of the organisation that created the project
  def organisation_membership
    OrganisationMembership.owners.where(organisation_uri: self.project.creator.to_s).first
  end

  def request
    @request ||= Request.new do |r|
      r.requestable  = self.project
      r.sender       = self.sender
      r.receiver     = self.organisation_membership
      r.request_type = 'project_request'
      r.data         = { project_membership_nature_uri: self.nature_uri }
    end
  end

  def save
    return false if invalid?

    self.request.save

    true
  rescue => e
    false
  end

  def persisted?  
    false  
  end

end```

Validate project request is not made for an existing project membership
user
```ruby
require 'active_model/model'

class ProjectRequest

  include ActiveModel::Model
  include ActiveModel::MassAssignmentSecurity

  attr_accessor :project_uri, :nature_uri, :sender, :organisation

  # TODO validate project isn't already member of project

  validates :project_uri, :nature_uri, presence: true
  validate :organisation_is_not_already_member_of_project

  def attributes=(values)
    sanitize_for_mass_assignment(values).each do |attr, value|
      public_send("#{attr}=", value)
    end
  end

  def project
    @project ||= Project.find(self.project_uri)
  end

  # Owner of the organisation that created the project
  def creator_organisation_owner_membership
    OrganisationMembership.owners.where(organisation_uri: self.project.creator.to_s).first
  end

  def request
    @request ||= Request.new do |r|
      r.requestable  = self.project
      r.sender       = self.sender
      r.receiver     = self.creator_organisation_owner_membership
      r.request_type = 'project_request'
      r.data         = { project_membership_nature_uri: self.nature_uri }
    end
  end

  def save
    return false if invalid?

    self.request.save

    true
  rescue => e
    false
  end

  def persisted?
    false
  end

  def existing_project_membership?
    project_membership_org_predicate = ProjectMembership.fields[:organisation].predicate.to_s
    project_membership_project_predicate = ProjectMembership.fields[:project].predicate.to_s

    ProjectMembership
      .where("?uri <#{project_membership_org_predicate}> <#{self.sender.organisation_resource.uri}>")
      .where("?uri <#{project_membership_project_predicate}> <#{self.project_uri}>")
      .count > 0
  end

  private

  def organisation_is_not_already_member_of_project
    errors.add(:project_uri, "already a member of this project") if existing_project_membership?
  end

end```
assistant