Merge pull request jashkenas#2620 from captbaritone/deep-invoke

Make _.invoke support deep method paths

test/collections.js

@@ -451,7 +451,7 @@
 
 
   QUnit.test('invoke', function(assert) {
-    assert.expect(5);
+    assert.expect(13);
     var list = [[5, 1, 7], [3, 2, 1]];
     var result = _.invoke(list, 'sort');
     assert.deepEqual(result[0], [1, 5, 7], 'first array sorted');
@@ -468,6 +468,38 @@
     assert.raises(function() {
       _.invoke([{a: 1}], 'a');
     }, TypeError, 'throws for non-functions');
+
+    var getFoo = _.constant('foo');
+    var getThis = function() { return this; };
+    var item = {
+      a: {
+        b: getFoo,
+        c: getThis,
+        d: null
+      },
+      e: getFoo,
+      f: getThis,
+      g: function() {
+        return {
+          h: getFoo
+        };
+      }
+    };
+    var arr = [item];
+    assert.deepEqual(_.invoke(arr, ['a', 'b']), ['foo'], 'supports deep method access via an array syntax');
+    assert.deepEqual(_.invoke(arr, ['a', 'c']), [item.a], 'executes deep methods on their direct parent');
+    assert.deepEqual(_.invoke(arr, ['a', 'd', 'z']), [void 0], 'does not try to access attributes of non-objects');
+    assert.deepEqual(_.invoke(arr, ['a', 'd']), [null], 'handles deep null values');
+    assert.deepEqual(_.invoke(arr, ['e']), ['foo'], 'handles path arrays of length one');
+    assert.deepEqual(_.invoke(arr, ['f']), [item], 'correct uses parent context with shallow array syntax');
+    assert.deepEqual(_.invoke(arr, ['g', 'h']), [void 0], 'does not execute intermediate functions');
+
+    arr = [{
+      a: function() { return 'foo'; }
+    }, {
+      a: function() { return 'bar'; }
+    }];
+    assert.deepEqual(_.invoke(arr, 'a'), ['foo', 'bar'], 'can handle different methods on subsequent objects');
   });
 
   QUnit.test('invoke w/ function reference', function(assert) {

underscore.js

@@ -146,6 +146,15 @@
     };
   };
 
+  var deepGet = function(obj, path) {
+    var length = path.length;
+    for (var i = 0; i < length; i++) {
+      if (obj == null) return void 0;
+      obj = obj[path[i]];
+    }
+    return length ? obj : void 0;
+  };
+
   // Helper for collection methods to determine whether a collection
   // should be iterated as an array or as an object.
   // Related: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
@@ -282,11 +291,24 @@
   };
 
   // Invoke a method (with arguments) on every item in a collection.
-  _.invoke = restArgs(function(obj, method, args) {
-    var isFunc = _.isFunction(method);
-    return _.map(obj, function(value) {
-      var func = isFunc ? method : value[method];
-      return func == null ? func : func.apply(value, args);
+  _.invoke = restArgs(function(obj, path, args) {
+    var contextPath, func;
+    if (_.isFunction(path)) {
+      func = path;
+    } else if (_.isArray(path)) {
+      contextPath = path.slice(0, -1);
+      path = path[path.length - 1];
+    }
+    return _.map(obj, function(context) {
+      var method = func;
+      if (!method) {
+        if (contextPath && contextPath.length) {
+          context = deepGet(context, contextPath);
+        }
+        if (context == null) return void 0;
+        method = context[path];
+      }
+      return method == null ? method : method.apply(context, args);
     });
   });
 
@@ -1382,15 +1404,6 @@
 
   _.noop = function(){};
 
-  var deepGet = function(obj, path) {
-    var length = path.length;
-    for (var i = 0; i < length; i++) {
-      if (obj == null) return void 0;
-      obj = obj[path[i]];
-    }
-    return length ? obj : void 0;
-  };
-
   _.property = function(path) {
     if (!_.isArray(path)) {
       return shallowProperty(path);