Added SELECT object mapping, convenience methods, fixed weakref usage after object death

lib/lpgar.rb

@@ -65,20 +65,53 @@ module LPGAR
 
       # Return either an existing Record or create a new one.
       # @param data [Hash{String => Object}] row data
-      def new(data)
+      # @param syncless [Boolean] do not perform any communication with PG
+      # @return [Object] new record object
+      def new(data, syncless: false)
         check_instantiable
         ident = Digest::MD5.hexdigest(data.values_at(*cols_pk).join)
-        if @instances[ident]
+        if @instances[ident] and @instances[ident].weakref_alive?
           @instances[ident].sync
           @instances[ident]
         end
 
         new_record = super(data)
-        create(new_record) unless new_record.sync
+        unless syncless
+          synced = new_record.sync
+          insert_query(new_record) unless synced
+        end
         track_instance(new_record)
         new_record
       end
 
+      # Explicitly create a new record. Returns nil if exists.
+      # @param data [Hash{String => Object}] row data
+      # @return [(Object,nil)] new record object or nil if exists
+      def create(data)
+        instance = new(data, syncless: true)
+        return if instance.sync
+
+        insert_query(instance)
+        instance
+      end
+
+      # Explicitly request an existing record. Returns nil if doesn't exist.
+      # @param data [Hash{String => Object}] row data
+      # @return [(Object,nil)] new record object or nil if doesn't exist.
+      def get(data)
+        instance = new(data, syncless: true)
+        instance if instance.sync
+      end
+
+      # Map returned rows from a query to an array of objects of this table.
+      # @param query [String] raw postgresql query
+      # @return [Array(Object)] array of records of this table
+      def map(query)
+        conn.exec(query).map do |row|
+          new(row, syncless: true)
+        end
+      end
+
       # Change row identity
       # Should not be called directly in most cases.
       # @param original [String] original row identity
@@ -91,15 +124,15 @@ module LPGAR
       # Create sync query.
       # @return [String]
       def sync_query
-        return @_memo_query if @_memo_query
+        return @sync_query if @sync_query
 
-        selector = @cols_pk.map.with_index do |pk, index|
-          "#{pk} = $#{index + 1}"
+        selector = @cols_pk.map.with_index do |key, index|
+          "#{key} = $#{index + 1}"
         end.join " AND "
-        @_memo_query = <<~QUERY
+        @sync_query = <<~QUERY
           SELECT * FROM #{@table_name}
           WHERE #{selector}
-          LIMIT 1
+          LIMIT 1;
         QUERY
       end
 
@@ -139,6 +172,8 @@ module LPGAR
       end
       # rubocop:enable Metrics/MethodLength, Metrics/AbcSize
 
+      private
+
       # Check if Record is properly set up.
       # @raise [StandardError] rasied if class is not properly set up
       def check_instantiable
@@ -166,7 +201,7 @@ module LPGAR
       end
 
       # Create a new record by "INSERT"
-      def create(record)
+      def insert_query(record)
         recbody = record.instance_variable_get("@data")
         # @sg-ignore
         conn.exec(<<~QUERY, recbody.values)
@@ -336,7 +371,7 @@ module LPGAR
         @conn = conn
         @instances = {}
       end
-      new_class.class_exec(&block)
+      new_class.class_exec(&block) if block
       new_class
     end
 

lpgar.gemspec

@@ -2,7 +2,7 @@
 
 Gem::Specification.new do |spec|
   spec.name                  = "lpgar"
-  spec.version               = "0.1"
+  spec.version               = "0.2"
   spec.summary               = "Lightweight Postgres Active Record"
   spec.description           = <<~DESC
     Lightweight implementation of Active Record pattern for Postgres.