Field comments

lib/angel_validate.dart

@@ -1,3 +1,4 @@
+export 'src/common_fields.dart';
 export 'src/field.dart';
 export 'src/form.dart';
 export 'src/form_renderer.dart';

lib/src/common_fields.dart

@@ -0,0 +1,50 @@
+import 'dart:async';
+import 'package:angel_framework/angel_framework.dart';
+import 'field.dart';
+import 'form_renderer.dart';
+
+/// A [Field] that accepts plain text.
+class TextField extends Field<String> {
+  /// If `true`, then renderers will produce a `<textarea>` element.
+  final bool isTextArea;
+
+  TextField(String name,
+      {String label, bool isRequired = false, this.isTextArea = false})
+      : super(name, label: label, isRequired: isRequired);
+
+  @override
+  FutureOr<U> accept<U>(FormRenderer<U> renderer) =>
+      renderer.visitTextField(this);
+
+  @override
+  FutureOr<FieldReadResult<String>> read(RequestContext req) {
+    var value = req.bodyAsMap[name] as String;
+    if (value == null) {
+      return null;
+    } else {
+      return FieldReadResult.success(value);
+    }
+  }
+}
+
+/// A [Field] that checks simply for its presence in the given data.
+/// Typically used for checkboxes.
+class BoolField extends Field<bool> {
+  BoolField(String name, {String label, bool isRequired = false})
+      : super(name, label: label, isRequired: isRequired);
+
+  @override
+  FutureOr<U> accept<U>(FormRenderer<U> renderer) =>
+      renderer.visitBoolField(this);
+
+  @override
+  FutureOr<FieldReadResult<bool>> read(RequestContext req) {
+    if (req.bodyAsMap.containsKey(name)) {
+      return FieldReadResult.success(true);
+    } else if (!isRequired) {
+      return FieldReadResult.success(false);
+    } else {
+      return null;
+    }
+  }
+}

lib/src/field.dart

@@ -3,31 +3,53 @@ import 'package:angel_framework/angel_framework.dart';
 import 'package:matcher/matcher.dart';
 import 'form_renderer.dart';
 
+/// Holds the result of validating a field.
 class FieldReadResult<T> {
+  /// If `true`, then validation was successful.
+  /// If `false`, [errors] must not be empty.
   final bool isSuccess;
+
+  /// The value provided by the user.
   final T value;
+
+  /// Any errors that arose during validation.
   final Iterable<String> errors;
 
   FieldReadResult.success(this.value)
       : isSuccess = true,
-        errors = null;
+        errors = [];
 
   FieldReadResult.failure(this.errors)
       : isSuccess = false,
         value = null;
 }
 
+/// An abstraction used to fetch values from request bodies, in a type-safe manner.
 abstract class Field<T> {
+  /// The name of this field. This is the name that users should include in
+  /// request bodies.
   final String name;
+
+  /// An optional label for the field.
   final String label;
+
+  /// Whether the field is required. If `true`, then if it is not
+  /// present, an error will be generated.
   final bool isRequired;
 
   Field(this.name, {this.label, this.isRequired = false});
 
+  /// Reads the value from the request body.
+  ///
+  /// If it returns `null` and [isRequired] is `true`, an error must
+  /// be generated.
   FutureOr<FieldReadResult<T>> read(RequestContext req);
 
+  /// Accepts a form renderer.
   FutureOr<U> accept<U>(FormRenderer<U> renderer);
 
+  /// Wraps this instance in one that throws an error if any of the
+  /// [matchers] fails.
   Field<T> match(Iterable<Matcher> matchers) => _MatchedField(this, matchers);
 }
 

lib/src/form_renderer.dart

@@ -1,6 +1,13 @@
 import 'dart:async';
+import 'common_fields.dart';
 import 'field.dart';
 
 abstract class FormRenderer<T> {
   const FormRenderer();
+
+  FutureOr<T> visit(Field<T> field) => field.accept(this);
+
+  FutureOr<T> visitBoolField(BoolField field);
+
+  FutureOr<T> visitTextField(TextField field);
 }