Fixes #2190 Implement a util.wrap function

spec/utilsBehaviors.js

@@ -29,6 +29,55 @@ describe('unwrapObservable', function() {
  });
 });
 
+describe('wrap', function() {
+ it('Should return an observable containing the non-observable parameter passed', function() {
+ var someObject = { abc: 123 },
+ primitiveValue = 123,
+ someFunction = function() { return primitiveValue; },
+ wrappedPrimitiveValue,
+ wrappedObject,
+ wrappedFunction,
+ wrappedNull,
+ wrappedUndefined;
+
+ wrappedObject = ko.utils.wrap(someObject);
+ expect(ko.isObservable(wrappedObject)).toBe(true);
+ expect(wrappedObject()).toBe(someObject);
+
+ wrappedPrimitiveValue = ko.utils.wrap(primitiveValue);
+ expect(ko.isObservable(wrappedPrimitiveValue)).toBe(true);
+ expect(wrappedPrimitiveValue()).toBe(123);
+
+ wrappedFunction = ko.utils.wrap(someFunction);
+ expect(ko.isObservable(wrappedFunction)).toBe(true);
+ expect(wrappedFunction()).toBe(someFunction);
+
+ wrappedNull = ko.utils.wrap(null);
+ expect(ko.isObservable(wrappedNull)).toBe(true);
+ expect(wrappedNull()).toBe(null);
+
+ wrappedUndefined = ko.utils.wrap(undefined);
+ expect(ko.isObservable(wrappedUndefined)).toBe(true);
+ expect(wrappedUndefined()).toBe(undefined);
+ });
+
+ it('Should return the same supplied observable', function() {
+ var someObject = { abc: 123 },
+ observablePrimitiveValue = ko.observable(123),
+ observableObjectValue = ko.observable(someObject),
+ observableNullValue = ko.observable(null),
+ observableUndefinedValue = ko.observable(undefined),
+ computedValue = ko.computed(function() { return observablePrimitiveValue() + 1; });
+
+ expect(ko.utils.wrap(observablePrimitiveValue)).toBe(observablePrimitiveValue);
+ expect(ko.utils.wrap(observableObjectValue)).toBe(observableObjectValue);
+ expect(ko.utils.wrap(observableNullValue)).toBe(observableNullValue);
+ expect(ko.utils.wrap(observableUndefinedValue)).toBe(observableUndefinedValue);
+ expect(ko.utils.wrap(computedValue)).toBe(computedValue);
+
+ });
+});
+
 describe('arrayForEach', function () {
  it('Should go call the callback for each element of the array, in order', function () {
  var callback = jasmine.createSpy('callback');

src/utils.js

@@ -426,6 +426,10 @@ ko.utils = (function () {
  return ko.isObservable(value) ? value() : value;
  },
 
+ wrap: function (value) {
+ return ko.isObservable(value) ? value : ko.observable(value);
+ },
+
  peekObservable: function (value) {
  return ko.isObservable(value) ? value.peek() : value;
  },
@@ -609,6 +613,7 @@ ko.exportSymbol('utils.unwrapObservable', ko.utils.unwrapObservable);
 ko.exportSymbol('utils.objectForEach', ko.utils.objectForEach);
 ko.exportSymbol('utils.addOrRemoveItem', ko.utils.addOrRemoveItem);
 ko.exportSymbol('utils.setTextContent', ko.utils.setTextContent);
+ko.exportSymbol('utils.wrap', ko.utils.wrap);
 ko.exportSymbol('unwrap', ko.utils.unwrapObservable); // Convenient shorthand, because this is used so commonly
 
 if (!Function.prototype['bind']) {