fix(core): allow user set new value

closes #58
closes #42
closes #29

Author: acrazing

src/__tests__/autobind-test.js

@@ -57,8 +57,7 @@ describe('autobind method decorator', function() {
     }, /@autobind decorator can only be applied to methods/);
   });
 
-
-  it('should not override binded instance method, while calling super method with the same name', function() { // eslint-disable-line max-len
+  it('should not override bound instance method, while calling super method with the same name', function() { // eslint-disable-line max-len
     class B extends A {
 
       @autobind
@@ -210,3 +209,56 @@ describe('autobind class decorator', function() {
     });
   });
 });
+
+describe('set new value', function() {
+  class A {
+    constructor() {
+      this.data = 'A';
+      this.foo = 'foo';
+      this.bar = 'bar';
+    }
+
+    @autobind
+    noop() {
+      return this.data;
+    }
+  }
+
+  const a = new A();
+
+  it('should not throw when reassigning to an object', function () {
+    a.noop = {
+      foo: 'bar'
+    };
+    assert.deepEqual(a.noop, {
+      foo: 'bar'
+    });
+    assert.equal(a.noop, a.noop);
+  });
+
+  it('should not throw when reassigning to a function', function() {
+    a.noop = function noop () {
+      return this.foo;
+    };
+    assert.equal(a.noop(), 'foo');
+    const noop = a.noop;
+    assert.equal(noop(), 'foo');
+    assert.equal(a.noop, a.noop);
+  });
+
+  it('should not throw when reassigning to a function again', function() {
+    a.noop = function noop2 () {
+      return this.bar;
+    };
+    assert(a.noop(), 'bar');
+    const noop2 = a.noop;
+    assert.equal(noop2(), 'bar');
+    assert.equal(a.noop, a.noop);
+  });
+
+  it('should not throw when reassigning to an object after bound a function', function() {
+    a.noop = {};
+    assert.deepEqual(a.noop, {});
+    assert.equal(a.noop, a.noop);
+  });
+});

src/index.js

@@ -73,19 +73,28 @@ function boundMethod(target, key, descriptor) {
   return {
     configurable: true,
     get() {
-      if (definingProperty || this === target.prototype || this.hasOwnProperty(key)) {
+      if (definingProperty || this === target.prototype || this.hasOwnProperty(key)
+        || typeof fn !== 'function') {
         return fn;
       }
 
       let boundFn = fn.bind(this);
       definingProperty = true;
       Object.defineProperty(this, key, {
-        value: boundFn,
         configurable: true,
-        writable: true
+        get() {
+          return boundFn;
+        },
+        set(value) {
+          fn = value;
+          delete this[key];
+        }
       });
       definingProperty = false;
       return boundFn;
+    },
+    set(value) {
+      fn = value;
     }
   };
 }