Scopes

Scoping allows you to specify commonly-used queries which can be referenced as a method which will return an ActiveRecord::Relation

In an example Product model with a product name attrubute we would put this inside the product.rb file(product model)

scope(:product_name, -> (name) { where("name like ?", "%#{name}%")})

where:

• :product_name is the method

• (name) is the argument we are passing

Every thing in the {} would be our Active Record Query where("name like ?", "%#{name}%") .

The % is a wild card. So putting a % on the start and end of the word will return everything that starts,ends and contains that word.

eg:

• %word% would return hword , hwordh , word , wordh

• %word would return hword, word

• word% would return word , wordh

• word would return word

calling out function

Product.product_name("some name")

Ths would evoke our active record query stated in our Product class.

Implementing this in Rails to create a search function

Searching a Product model

scope(:product_name, -> (name) { where("name like ?", "%#{name}%")})
scope(:description, -> (description) { where("description like ?", "%#{description}%")})
scope(:price, -> (price) { where price: price })

In our products controller we need to allow the params through, create method under private

def filtering_params(params)
   params.slice(:product_name, :description, :price)
end

In our index method

def index
    @products = Product.all
    filtering_params(params).each do |key, value|
      @products = @products.public_send(key, value) if value.present?
    end
end

We iterate through the params dictionary and to get key value pairs and pass them into the .public_send() method which evokes the method key and passes in the attribute value. This will then run the corresponding method defined in our products class and return an ActiveRecord::Relation which we save to the @products model

Do get these params we can pass in a form to the index view that takes in the :product_name, :description, :price

<div class="panel panel-default">
  <div class="panel-body">
    <form class="form-inline">
      <div class="form-group">
        <label for="product_name">Name:</label>
        <input type="text" name="product_name"  class="form-control">
      </div>
      <div class="form-group">
        <label for="description">Description:</label>
        <input type="text" name="description" class="form-control">
      </div>
      <div class="form-group">
        <label for="price">Price:</label>
        <input type="text" name="price" class="form-control">
      </div>
      <input type="submit" value="Filter" class="btn btn-default">
    </form>
  </div>
</div>