Add CompositeDisposable::addIfDisposable

spec/composite-disposable-spec.coffee

@@ -29,3 +29,13 @@ describe "CompositeDisposable", ->
     expect(disposable1.disposed).toBe true
     expect(disposable2.disposed).toBe false
     expect(disposable3.disposed).toBe true
+
+  describe "::addIfDisposable(disposables...)", ->
+    it "ignores disposables without a ::dispose function", ->
+      composite = new CompositeDisposable
+      composite.addIfDisposable(disposable1, undefined, null)
+      composite.addIfDisposable(whatever: ->)
+
+      composite.dispose()
+
+      expect(disposable1.disposed).toBe true

src/composite-disposable.coffee

@@ -57,6 +57,18 @@ class CompositeDisposable
       @disposables.add(disposable) for disposable in arguments
     return
 
+  # Public: Add a disposable to be disposed when the composite is disposed,
+  # ignoring it if it does not implement `.dispose()`.
+  #
+  # See {CompositeDisposable::add} documentation for further information.
+  #
+  # * `disposable` {Disposable} instance or any object with a `.dispose()`
+  #   method.
+  addIfDisposable: ->
+    for disposable in arguments
+      @add(disposable) if typeof disposable?.dispose is "function"
+    return
+
   # Public: Remove a previously added disposable.
   #
   # * `disposable` {Disposable} instance or any object with a `.dispose()`