Expression for evaluating feature ids

src/ol/expr/expression.js

@@ -96,6 +96,7 @@ ol.expr.lib = {};
  */
 ol.expr.functions = {
   EXTENT: 'extent',
+  FID: 'fid',
   GEOMETRY_TYPE: 'geometryType'
 };
 
@@ -119,8 +120,27 @@ ol.expr.lib[ol.expr.functions.EXTENT] = function(minX, maxX, minY, maxY) {
   return intersects;
 };
 
+
+/**
+ * Determine if the feature identifier matches any of the provided values.
+ * @param {...string} var_args Feature identifiers.
+ * @return {boolean} The feature's identifier matches one of the given values.
+ * @this {ol.Feature}
+ */
+ol.expr.lib[ol.expr.functions.FID] = function(var_args) {
+  var matches = false;
+  var id = this.getFeatureId();
+  if (goog.isDef(id)) {
+    for (var i = 0, ii = arguments.length; i < ii; ++i) {
+      if (arguments[i] === id) {
+        matches = true;
+        break;
+      }
     }
   }
+  return matches;
+};
+
 
 /**
  * Determine if a feature's default geometry is of the given type.

test/spec/ol/expr/expression.test.js

@@ -663,6 +663,54 @@ describe('ol.expr.lib', function() {
 
   });
 
+  describe('fid()', function() {
+
+    var one = new ol.Feature();
+    one.setFeatureId('one');
+
+    var two = new ol.Feature();
+    two.setFeatureId('two');
+
+    var three = new ol.Feature();
+    three.setFeatureId('three');
+
+    var four = new ol.Feature();
+    four.setFeatureId('four');
+
+    var odd = parse('fid("one", "three")');
+    var even = parse('fid("two", "four")');
+    var first = parse('fid("one")');
+    var last = parse('fid("four")');
+    var none = parse('fid("foo")');
+
+    it('evaluates to true if feature id matches', function() {
+      expect(evaluate(odd, one), true);
+      expect(evaluate(odd, three), true);
+      expect(evaluate(even, two), true);
+      expect(evaluate(even, four), true);
+      expect(evaluate(first, one), true);
+      expect(evaluate(last, four), true);
+    });
+
+    it('evaluates to false if feature id doesn\'t match', function() {
+      expect(evaluate(odd, two), false);
+      expect(evaluate(odd, four), false);
+      expect(evaluate(even, one), false);
+      expect(evaluate(even, three), false);
+      expect(evaluate(first, two), false);
+      expect(evaluate(first, three), false);
+      expect(evaluate(first, four), false);
+      expect(evaluate(last, one), false);
+      expect(evaluate(last, two), false);
+      expect(evaluate(last, three), false);
+      expect(evaluate(none, one), false);
+      expect(evaluate(none, two), false);
+      expect(evaluate(none, three), false);
+      expect(evaluate(none, four), false);
+    });
+
+  });
+
   describe('geometryType()', function() {
 
     var point = new ol.Feature({