Add some utility methods to Relation

js/id/graph/relation.js

@@ -18,6 +18,26 @@ iD.Relation = iD.Entity.extend({
         return 'relation';
     },
 
+    // Return the first member with the given role. A copy of the member object
+    // is returned, extended with an 'index' property whose value is the member index.
+    memberByRole: function(role) {
+        for (var i = 0; i < this.members.length; i++) {
+            if (this.members[i].role === role) {
+                return _.extend({}, this.members[i], {index: i});
+            }
+        }
+    },
+
+    // Return the first member with the given id. A copy of the member object
+    // is returned, extended with an 'index' property whose value is the member index.
+    memberById: function(id) {
+        for (var i = 0; i < this.members.length; i++) {
+            if (this.members[i].id === id) {
+                return _.extend({}, this.members[i], {index: i});
+            }
+        }
+    },
+
     // Returns an array [A0, ... An], each Ai being an array of node arrays [Nds0, ... Ndsm],
     // where Nds0 is an outer ring and subsequent Ndsi's (if any i > 0) being inner rings.
     //

js/id/svg/member_classes.js

@@ -19,7 +19,7 @@ iD.svg.MemberClasses = function(graph) {
 
             relations.forEach(function (relation) {
                 classes += ' member-type-' + relation.tags.type;
-                classes += ' member-role-' + _.find(relation.members, function (member) { return member.id == d.id; }).role;
+                classes += ' member-role-' + relation.memberById(d.id).role;
             });
 
             classes = classes.trim();

test/spec/graph/relation.js

@@ -55,6 +55,40 @@ describe('iD.Relation', function () {
         });
     });
 
+    describe("#geometry", function () {
+        it("returns 'relation'", function () {
+            expect(iD.Relation().geometry()).to.equal('relation');
+        });
+    });
+
+    describe("#memberByRole", function () {
+        it("returns the first member with the given role", function () {
+            var r = iD.Relation({members: [
+                {id: 'a', role: 'inner'},
+                {id: 'b', role: 'outer'},
+                {id: 'c', role: 'outer'}]});
+            expect(r.memberByRole('outer')).to.eql({id: 'b', role: 'outer', index: 1});
+        });
+
+        it("returns undefined if no members have the given role", function () {
+            expect(iD.Relation().memberByRole('outer')).to.be.undefined;
+        });
+    });
+
+    describe("#memberById", function () {
+        it("returns the first member with the given id", function () {
+            var r = iD.Relation({members: [
+                {id: 'a', role: 'outer'},
+                {id: 'b', role: 'outer'},
+                {id: 'b', role: 'inner'}]});
+            expect(r.memberById('b')).to.eql({id: 'b', role: 'outer', index: 1});
+        });
+
+        it("returns undefined if no members have the given role", function () {
+            expect(iD.Relation().memberById('b')).to.be.undefined;
+        });
+    });
+
     describe("#multipolygon", function () {
         specify("single polygon consisting of a single way", function () {
             var a = iD.Node(),