Add Field class

README.md

@@ -164,8 +164,6 @@ schema.primary_keys
 #=> ["id"]
 schema.foreign_keys
 #=> [{"fields" => "state", "reference" => { "datapackage" => "http://data.okfn.org/data/mydatapackage/", "resource" => "the-resource", "fields" => "state_id" } } ]
-schema.cast('height', '10')
-#=> 10.0
 schema.get_field('id')
 #=> {"name"=>"id", "constraints"=>{"required"=>true}, "type"=>"string", "format"=>"default"}
 schema.has_field?('foo')
@@ -176,13 +174,13 @@ schema.get_fields_by_type('string')
 #=> [{"name"=>"id", "constraints"=>{"required"=>true}, "type"=>"string", "format"=>"default"}, {"name"=>"height", "type"=>"string", "format"=>"default"}]
 schema.get_constraints('id')
 #=> {"required" => true}
-schema.convert_row(['string', '10.0'])
+schema.cast_row(['string', '10.0'])
 #=> ['string', 10.0]
-schema.convert([['foo', '12.0'],['bar', '10.0']])
+schema.cast([['foo', '12.0'],['bar', '10.0']])
 #=> [['foo', 12.0],['bar', 10.0]]
 ```
 
-When converting a row (using `convert_row`), or a number of rows (using `convert`), by default the converter will fail on the first error it finds. If you pass `false` as the second argument, the errors will be collected into a `errors` attribute for you to review later. For example:
+When casting a row (using `cast_row`), or a number of rows (using `cast`), by default the converter will fail on the first error it finds. If you pass `false` as the second argument, the errors will be collected into a `errors` attribute for you to review later. For example:
 
 ```ruby
 schema_hash = {
@@ -209,14 +207,31 @@ rows = [
   ['wrong column count']
 ]
 
-schema.convert(rows)
+schema.cast(rows)
 #=> JsonTableSchema::InvalidCast: notanumber is not a number
-schema.convert(rows, false)
+schema.cast(rows, false)
 #=> JsonTableSchema::MultipleInvalid
 schema.errors
 #=> [#<JsonTableSchema::InvalidCast: notanumber is not a number>, #<JsonTableSchema::InvalidCast: notanumber is not a number>, #<JsonTableSchema::ConversionError: The number of items to convert (1) does not match the number of headers in the schema (2)>]
 ```
 
+## Field
+
+```ruby
+# Init field
+field = JsonTableSchema::Field.new({'type': 'number'})
+
+# Cast a value
+field.cast_value('12345')
+#=> 12345.0
+```
+
+Data values can be cast to native Ruby objects with a Field instance. Type instances can be initialized with f[ield descriptors](http://dataprotocols.org/json-table-schema/#field-descriptors). This allows formats and constraints to be defined.
+
+Casting a value will check the value is of the expected type, is in the correct format, and complies with any constraints imposed by a schema. E.g. a date value (in ISO 8601 format) can be cast with a DateType instance. Values that can't be cast will raise an `InvalidCast` exception.
+
+Casting a value that doesn't meet the constraints will raise a `ConstraintError` exception.
+
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
@@ -227,7 +242,6 @@ To install this gem onto your local machine, run `bundle exec rake install`. To
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/jsontableschema. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
 
-
 ## License
 
 The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).

lib/jsontableschema.rb

@@ -28,6 +28,7 @@
 require "jsontableschema/types/string"
 require "jsontableschema/types/time"
 
+require "jsontableschema/field"
 require "jsontableschema/validate"
 require "jsontableschema/model"
 require "jsontableschema/data"

lib/jsontableschema/data.rb

@@ -3,11 +3,15 @@ module Data
 
     attr_reader :errors
 
-    def convert(rows, fail_fast = true)
+    def load_fields!
+      self['fields'] = (self['fields'] || []).map { |f| JsonTableSchema::Field.new(f) }
+    end
+
+    def cast(rows, fail_fast = true)
       @errors ||= []
       rows.map! do |r|
         begin
-          convert_row(r, fail_fast)
+          cast_row(r, fail_fast)
         rescue MultipleInvalid, ConversionError => e
           raise e if fail_fast == true
           @errors << e if e.is_a?(ConversionError)
@@ -17,19 +21,19 @@ def convert(rows, fail_fast = true)
       rows
     end
 
-    def convert_row(row, fail_fast = true)
+    alias_method :convert, :cast
+
+    def cast_row(row, fail_fast = true)
       @errors ||= []
       raise_header_error(row) if row.count != fields.count
       fields.each_with_index do |field,i|
-        row[i] = convert_column(row[i], field, fail_fast)
+        row[i] = cast_column(field, row[i], fail_fast)
       end
       check_for_errors
       row
     end
 
-    def cast(field_name, value)
-      convert_column(value, get_field(field_name), true)
-    end
+    alias_method :convert_row, :cast_row
 
     private
 
@@ -41,10 +45,8 @@ def check_for_errors
       raise(JsonTableSchema::MultipleInvalid.new("There were errors parsing the data")) if @errors.count > 0
     end
 
-    def convert_column(col, field, fail_fast)
-      klass = get_class_for_type(field['type'] || 'string')
-      converter = Kernel.const_get(klass).new(field)
-      converter.cast(col)
+    def cast_column(field, col, fail_fast)
+      field.cast_value(col)
     rescue Exception => e
       if fail_fast == true
         raise e
@@ -53,5 +55,7 @@ def convert_column(col, field, fail_fast)
       end
     end
 
+    alias_method :convert_column, :cast_column
+
   end
 end

lib/jsontableschema/field.rb

@@ -0,0 +1,41 @@
+module JsonTableSchema
+  class Field < Hash
+    include JsonTableSchema::Helpers
+
+    attr_reader :type_class
+
+    def initialize(descriptor)
+      self.merge! descriptor
+      @type_class = get_type
+    end
+
+    def name
+      self['name']
+    end
+
+    def type
+      self['type'] || 'string'
+    end
+
+    def format
+      self['format'] || 'default'
+    end
+
+    def constraints
+      self['constraints'] || {}
+    end
+
+    def cast_value(col)
+      klass = get_class_for_type(type)
+      converter = Kernel.const_get(klass).new(self)
+      converter.cast(col)
+    end
+
+    private
+
+      def get_type
+        Object.const_get get_class_for_type(type)
+      end
+
+  end
+end

lib/jsontableschema/helpers.rb

@@ -22,7 +22,7 @@ def false_values
     end
 
     def get_class_for_type(type)
-      "JsonTableSchema::Types::#{type_class_lookup[type]}"
+      "JsonTableSchema::Types::#{type_class_lookup[type] || 'String'}"
     end
 
     def type_class_lookup

lib/jsontableschema/model.rb

@@ -53,10 +53,6 @@ def get_fields_by_type(type)
 
     private
 
-      def fields
-        self['fields']
-      end
-
       def transform(name)
         name.downcase! if @opts[:case_insensitive_headers]
         name

lib/jsontableschema/schema.rb

@@ -5,26 +5,27 @@ class Schema < Hash
     include JsonTableSchema::Data
     include JsonTableSchema::Helpers
 
-    def initialize(schema, opts = {})
-      self.merge! parse_schema(schema)
+    def initialize(descriptor, opts = {})
+      self.merge! parse_schema(descriptor)
       @messages = []
       @opts = opts
+      load_fields!
       load_validator!
       expand!
     end
 
-    def parse_schema(schema)
-      if schema.class == Hash
-        schema
-      elsif schema.class == String
+    def parse_schema(descriptor)
+      if descriptor.class == Hash
+        descriptor
+      elsif descriptor.class == String
         begin
-          JSON.parse open(schema).read
+          JSON.parse open(descriptor).read
         rescue Errno::ENOENT
-          raise SchemaException.new("File not found at `#{schema}`")
+          raise SchemaException.new("File not found at `#{descriptor}`")
         rescue OpenURI::HTTPError => e
-          raise SchemaException.new("URL `#{schema}` returned #{e.message}")
+          raise SchemaException.new("URL `#{descriptor}` returned #{e.message}")
         rescue JSON::ParserError
-          raise SchemaException.new("File at `#{schema}` is not valid JSON")
+          raise SchemaException.new("File at `#{descriptor}` is not valid JSON")
         end
       else
         raise SchemaException.new("A schema must be a hash, path or URL")

lib/jsontableschema/table.rb

@@ -7,10 +7,10 @@ def self.infer_schema(csv, opts = {})
       JsonTableSchema::Table.new(csv, nil, opts)
     end
 
-    def initialize(csv, schema, opts = {})
+    def initialize(csv, descriptor, opts = {})
       @opts = opts
       @csv = parse_csv(csv)
-      @schema = schema.nil? ? infer_schema(@csv) : JsonTableSchema::Schema.new(schema)
+      @schema = descriptor.nil? ? infer_schema(@csv) : JsonTableSchema::Schema.new(descriptor)
     end
 
     def parse_csv(csv)
@@ -25,7 +25,7 @@ def csv_options
     def rows(opts = {})
       fail_fast = opts[:fail_fast] || opts[:fail_fast].nil?
       rows = opts[:limit] ? @csv.to_a.drop(1).take(opts[:limit]) : @csv.to_a.drop(1)
-      converted = @schema.convert(rows, fail_fast)
+      converted = @schema.cast(rows, fail_fast)
       opts[:keyed] ? coverted_to_hash(@csv.headers, converted) : converted
     end
 

lib/jsontableschema/version.rb

@@ -1,3 +1,3 @@
 module JsonTableSchema
-  VERSION = "0.1.0"
+  VERSION = "0.2.0"
 end