initial draft

0000-improved-cp-syntax.md

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+- Start Date: 2014-19-30
+- RFC PR: (leave this empty)
+- Ember Issue: (leave this empty)
+
+# Summary
+
+Improve computed property syntax
+
+# Motivation
+
+Today, the setter variant of CP's is both confusing, and looks scary as sin.
+(To many concepts must be taught and it is to easy to screw it up.)
+
+# Detailed design
+
+today:
+------
+
+```js
+fullName: Ember.computed('firstName', 'lastName', function(key, value) {
+  if (arguments.length > 1) {
+    var names = value.split(' ');
+    this.setProperties({
+      firstName: names[0],
+      lastName: names[1]
+    });
+    return value;
+  }
+
+  return this.get('firstName') + ' ' + this.get('lastName');
+});
+```
+
+Tomorrow:
+---------
+
+```js
+fullName: Ember.computed('firstName', 'lastName', {
+  get(keyName) {
+    return this.get('firstName') + ' ' + this.get('lastName');
+  },
+
+  set(keyName, fullName) {
+   var names = fullName.split(' ');
+
+   this.setProperties({
+     firstName: names[0],
+     lastName: names[1]
+   });
+
+   return fullName;
+  }
+});
+```
+
+
+Notes:
+------
+
+* we should likely keep `Ember.computed(fn);`  as shorthand for getter only
+Migration:
+* Also, `get` xor `set` variants would also be possible.
+* `{ get() { } }`  is es6 syntax for `{ get: function() { } )`
+
+Migration
+---------
+
+* 1.x support both, detect new behaviour by testing if the last arg is not null and typeof object
+* 1.x+1 deprecate if last arg is a function and its arity is greater then 1
+
+
+# Drawbacks
+
+N/A
+
+# Alternatives
+
+N/A
+
+# Unresolved questions
+
+* do setters with the new syntax get the 3rd arg of `oldValue` provided?