add default_attributes

README.md

@@ -67,8 +67,8 @@ song.update! year: 1988, artist: 'Metallica'  # this variant also saves
 
 ### Restricting / allowing certain attributes
 
-You may specify required arguments. Records without these attributes will
-not be saved. Note that `id` is always required
+You may specify required attributes. Records without these attributes will
+not be saved. Note that `id` is always required.
 
 ```ruby
 class Song < ActiveCabinet
@@ -114,6 +114,22 @@ song.valid?  # => false
 song.error   # => "invalid attributes: [:artist]"
 ```
 
+### Declaring default attribute values
+
+You may specify default values for some attributes. These attrributes will
+be merged into newly created record instances.
+
+```ruby
+class Song < ActiveCabinet
+  required_attributes :title
+  default_attributes format: :mp3
+end
+
+song = Song.new title: "Moonchild"
+song.format   # => :mp3
+```
+
+
 ### Configuring storage path
 
 By default, `ActiveCabinet` stores all its files (two files per model) in the

lib/active_cabinet.rb

@@ -14,7 +14,7 @@ class ActiveCabinet
   #
   # @param [Hash] attributes record attributes
   def initialize(attributes = {})
-    @attributes = attributes.transform_keys(&:to_sym)
+    @attributes = default_attributes.merge attributes.transform_keys(&:to_sym)
   end
 
   # @!group Attribute Management
@@ -42,6 +42,10 @@ def optional_attributes
     self.class.optional_attributes
   end
 
+  def default_attributes
+    self.class.default_attributes
+  end
+
   # Returns +true+ if the object is valid.
   # 
   # @return [Boolean] +true+ if the record is valid.
@@ -63,6 +67,23 @@ def valid?
     true
   end
 
+  # @!group Attribute Accessors
+
+  # Returns the attribute value for the given key.
+  #
+  # @return [Object] the attribute value.
+  def [](key)
+    attributes[key]
+  end
+
+  # Sets the attribute value for the given key.
+  #
+  # @param [Symbol] key the attribute key.
+  # @param [Object] value the attribute value.
+  def []=(key, value)
+    attributes[key] = value
+  end
+
   # @!group Dynamic Attribute Accessors
 
   # Provides read/write access to {attributes}

lib/active_cabinet/metaclass.rb

@@ -69,18 +69,46 @@ def all_attributes
     end
 
     # Returns an array of records for which the block returns true.
+    # When +query+ is provided, it should be a Hash with a single key and
+    # value. The result will be records that have a matching attribute.
+    #
+    # @example Search using a Hash query
+    #   Song.where artist: "Iron Maiden"
+    #
+    # @example Search using a block
+    #   Song.where { |record| record[:artist] == "Iron Maiden" }
     #
     # @yieldparam [Object] record all record instances.
-    def where
-      all.select { |record| yield record }
+    # @return [Array<Object>] record all record instances.
+    def where(query = nil)
+      if query
+        key, value = query.first
+        all.select { |record| record[key] == value }
+      else
+        all.select { |record| yield record }
+      end
     end
 
     # Returns the record matching the +id+.
+    # When providing a Hash with a single key-value pair, it will return the
+    # first matching object from the respective {where} query.
+    #
+    # @example Retrieve a record by ID
+    #   Song.find 1
+    #   Song[1]
+    #
+    # @example Retrieve a different attributes
+    #   Song.find artist: "Iron Maiden"
+    #   Song[artist: "Iron Maiden"]
     #
     # @return [Object, nil] the object if found, or +nil+.
     def find(id)
-      attributes = cabinet[id]
-      attributes ? new(attributes) : nil
+      if id.is_a? Hash
+        where(id).first
+      else
+        attributes = cabinet[id]
+        attributes ? new(attributes) : nil
+      end
     end
     alias [] find
 
@@ -101,11 +129,13 @@ def drop
 
     # @!group Attribute Management
 
-    # Returns an array containing {required_attributes} and {optional_attributes}.
+    # Returns an array containing the keys of all allowed attributes as
+    # defined by {required_attributes}, {optional_attributes} and 
+    # {default_attributes}.
     #
     # @return [Array<Symbol>] array of required attribute keys.
     def allowed_attributes
-      (optional_attributes || []) + required_attributes
+      (optional_attributes || []) + required_attributes + default_attributes.keys
     end
 
     # Sets the required record attribute names.
@@ -138,6 +168,18 @@ def optional_attributes(*args)
       end
     end
 
+    # Sets the default record attribute values.
+    #
+    # @param [Hash<Symbol, Object>] **attributes one or more attribute names and values.
+    # @return [Hash<Symbol, Object>] the hash of the default attributes.
+    def default_attributes(args = nil)
+      if args
+        @default_attributes = args
+      else
+        @default_attributes ||= {}
+      end
+    end
+
     # @!group Utilities
 
     # Returns all records as a hash, with record IDs as the keys.

spec/active_cabinet/active_cabinet_metaclass_spec.rb

@@ -39,7 +39,7 @@
 
   describe '::allowed_attributes' do
     it "returns an array of required and optional attributes" do
-      expect(subject.allowed_attributes).to match_array([:id, :title, :artist, :album])
+      expect(subject.allowed_attributes).to match_array([:id, :title, :artist, :album, :format])
     end
   end
 
@@ -131,7 +131,14 @@
 
     context "when the record is not found" do
       it "returns nil" do
-        expect(subject.find(11)).to be_nil
+        expect(subject.find 11).to be_nil
+      end
+    end
+
+    context "when a hash is given" do
+      it "returns the first matching object via #where" do
+        result = subject.find title: "Master of Puppets"
+        expect(result).to be_a Song
       end
     end
   end
@@ -179,7 +186,7 @@
 
     context "with arguments" do
       before { @original = subject.required_attributes }
-      after  { subject.required_attributes @original}
+      after  { subject.required_attributes @original }
 
       it "sets the required attributes and always adds :id" do
         subject.required_attributes :cake, :pizza
@@ -188,6 +195,24 @@
     end
   end
 
+  describe '::default_attributes', :focus do
+    context "without arguments" do
+      it "returns the default arguments hash" do
+        expect(subject.default_attributes).to eq(format: :mp3)
+      end
+    end
+
+    context "with arguments" do
+      before { @original = subject.default_attributes }
+      after  { subject.default_attributes @original }
+
+      it "sets the default attributes" do
+        subject.default_attributes media: :cd
+        expect(subject.default_attributes).to eq({media: :cd})
+      end
+    end
+  end
+
   describe '::size' do
     it "returns the number of records" do
       expect(subject.size).to eq 10
@@ -203,10 +228,20 @@
   end
 
   describe '::where' do
-    it "returns records matching the block" do
-      result = subject.where { |asset| asset.id > 7 }
-      expect(result.count).to eq 3
-      expect(result.map { |asset| asset.id }).to match_array [8, 9, 10]
+    context "when no query is provided" do
+      it "returns records matching the block" do
+        result = subject.where { |asset| asset.id > 7 }
+        expect(result.count).to eq 3
+        expect(result.map { |asset| asset.id }).to match_array [8, 9, 10]
+      end
+    end
+
+    context "when a query is provided" do
+      it "returns records matching the key => value pair" do
+        result = subject.where title: "Master of Puppets"
+        expect(result.count).to eq 10
+        expect(result.first).to be_a Song
+      end
     end
   end
 end

spec/active_cabinet/active_cabinet_spec.rb

@@ -47,9 +47,22 @@
     end
   end
 
+  describe '#[]' do
+    it "returns the attribute value" do
+      expect(subject[:title]).to eq "Red Balloons"
+    end
+  end
+
+  describe '#[]=' do
+    it "sets the attribute value" do
+      subject[:title] = "Moonchild"
+      expect(subject.title).to eq "Moonchild"
+    end
+  end
+
   describe '#allowed_attributes' do
     it "returns an array of required and optional attributes" do
-      expect(subject.allowed_attributes).to match_array [:album, :artist, :id, :title]
+      expect(subject.allowed_attributes).to match_array [:album, :artist, :id, :title, :format]
     end
   end
 

spec/mocks/song.rb

@@ -1,6 +1,7 @@
 module Mocks
   class Song < ActiveCabinet
     required_attributes :title
+    default_attributes format: :mp3
     optional_attributes :artist, :album
 
     class << self