From 3fa1ae3bc43045efed263d78754c050fd6cfe000 Mon Sep 17 00:00:00 2001
From: Nik Krimm <nkrimm@signal.co>
Date: Wed, 4 May 2016 14:03:17 -0500
Subject: [PATCH] Add _.method as peer to _.property for capturing return
 values of functions on an Object.  Closes #2286: Underscore could use a
 _.propertyResult.

---
 test/utility.js | 12 ++++++++++++
 underscore.js   | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/test/utility.js b/test/utility.js
index 6a81e8735..0f1a8c4ca 100644
--- a/test/utility.js
+++ b/test/utility.js
@@ -95,6 +95,18 @@
     assert.equal(undefPropertyOf('curly'), void 0, 'should return undefined when obj is undefined');
   });
 
+  QUnit.test('method', function(assert) {
+    var stooge = {name: function() { return 'moe'; }, sum: function(a, b, c) { return a + b + c; }};
+    assert.equal(_.method('name')(stooge), 'moe', 'should return the results of calling the method with the given name');
+    assert.equal(_.method('sum')(stooge, 1, 2, 3), 6, 'should pass rest of arguments to named method for evaluation');
+    assert.equal(_.method(function() { return this.name(); })(stooge), 'moe', 'should apply a function literal passed.');
+    assert.equal(_.method(function(a, b, c) { return this.sum(a, b, c); })(stooge, 1, 2, 3), 6, 'should pass arguments when applying a function literal.');
+    assert.equal(_.method('macerena')(stooge), void 0, 'should return undefined for non-existant method name on defined object');
+    assert.equal(_.method('name')(null), void 0, 'should return undefined for null object');
+    assert.equal(_.method()(stooge), void 0, 'should return undefined for undefined method name on existing object');
+    assert.equal(_.method()(void 0), void 0, 'should return undefined for undefined method name on undefined object');
+  });
+
   QUnit.test('random', function(assert) {
     var array = _.range(1000);
     var min = Math.pow(2, 31);
diff --git a/underscore.js b/underscore.js
index 4a0cf6e73..7eb3b0675 100644
--- a/underscore.js
+++ b/underscore.js
@@ -1370,6 +1370,21 @@
 
   _.property = property;
 
+  // Generates a function for a given object that returns the passed function's return value.
+  // Accepts a method name or function literal for value.
+  // If value is a string, function assumes this string is a method name on the
+  // referenced object.
+  _.method = function(value) {
+    return restArgs(function(obj, args) {
+      if (obj == null) { return; }
+      var func = _.isFunction(value) ? value : obj[value];
+      if (func) {
+        return func.apply(obj, args);
+      }
+    });
+  };
+
+
   // Generates a function for a given object that returns a given property.
   _.propertyOf = function(obj) {
     return obj == null ? function(){} : function(key) {