accepting a custom isEqual function

README.md

@@ -16,9 +16,16 @@ Includes
 
 ## Model API
 
-###Bacon.Model(initValue)
+###Bacon.Model(initValue [, options])
+
+Creates a new model, with the given (optional) initial value. The optional `options` argument is an object that
+currently accepts the following field:
+
+`isEqual` (optional) : a two-arg function that should return true iff its two arguments are to be considered
+equal values, and return false otherwise. This is used for implicitly
+[skipping duplicates](https://github.com/baconjs/bacon.js/#property-skipduplicates).
+This defaults to `===` comparison.
 
-Creates a new model, with the given (optional) initial value.
 
 ###model.set(value)
 

dist/bacon.model.js

@@ -31,10 +31,13 @@
         return !a.initial && eq(a.value, b.value);
       };
     };
-    Model = Bacon.Model = function(initValue) {
+    Model = Bacon.Model = function(initValue, options) {
       var currentValue, eq, model, modificationBus, myId, myModCount, syncBus, valueWithSource;
+      if (options == null) {
+        options = {};
+      }
       myId = idCounter++;
-      eq = defaultEquals;
+      eq = options.isEqual || defaultEquals;
       myModCount = 0;
       modificationBus = new Bacon.Bus();
       syncBus = new Bacon.Bus();
@@ -128,7 +131,7 @@
         return lensed;
       };
       model.syncConverter = id;
-      if (arguments.length >= 1) {
+      if (arguments.length === 1 || arguments.length > 1 && typeof arguments[0] !== 'undefined') {
         model.set(initValue);
       }
       return model;

src/bacon.model.coffee

@@ -13,9 +13,9 @@ init = (Bacon) ->
   defaultEquals = (a, b) -> a == b
   sameValue = (eq) -> (a, b) -> !a.initial && eq(a.value, b.value)
 
-  Model = Bacon.Model = (initValue) ->
+  Model = Bacon.Model = (initValue, options = {}) ->
     myId = idCounter++
-    eq = defaultEquals
+    eq = options.isEqual || defaultEquals
     myModCount = 0
     modificationBus = new Bacon.Bus()
     syncBus = new Bacon.Bus()
@@ -67,7 +67,7 @@ init = (Bacon) ->
         valueLens.set(e, lens.get(e.value))))
       lensed
     model.syncConverter = id
-    if (arguments.length >= 1)
+    if (arguments.length == 1 || arguments.length > 1 && typeof arguments[0] != 'undefined')
       model.set initValue
     model
 

test/bacon.model.spec.coffee

@@ -50,7 +50,7 @@ describe "Model initial value", ->
   it "is sent", ->
     cylinders = lib.Model(12)
     expect(collect(cylinders)).to.deep.equal([12])
-  it "handles undefined like any other value", ->
+  it "handles undefined like any other value if no second argument is given", ->
     cylinders = lib.Model(undefined)
     expect(collect(cylinders)).to.deep.equal([undefined])
   it "can be omitted", ->
@@ -320,6 +320,22 @@ describe "Model.combine", ->
       { a: "a", b: "b" },
       { a: "a2", b: "b" }])
 
+
+customEquals = (a, b) -> a.x == b.x && a.y == b.y
+
+describe "Model with custom isEqual function", ->
+  it "ignores object duplicates from input by custom equality", ->
+    b = lib.Model(undefined, { isEqual: customEquals })
+    values = collect(b)
+    b.addSource(Bacon.fromArray([{ x: 0, y: 0 }, { x: 1, y: 0 }, { x: 1, y: 0 }]))
+    expect(values).to.deep.equal([{ x: 0, y: 0 }, { x: 1, y: 0 }])
+  it "ignores object duplicates from input with init value by custom equality", ->
+    b = lib.Model({ x: 0, y: 0 }, { isEqual: customEquals })
+    values = collect(b)
+    b.addSource(Bacon.fromArray([{ x: 0, y: 0 }, { x: 1, y: 0 }, { x: 1, y: 0 }]))
+    expect(values).to.deep.equal([{ x: 0, y: 0 }, { x: 1, y: 0 }])
+
+
 collect = (observable) ->
   values = []
   observable.onValue (value) ->