1. function proxy (target, sourceKey, key) {
    2.   sharedPropertyDefinition.get = function proxyGetter () {
    3.     return this[sourceKey][key] // <==
    4.   };
    5.   sharedPropertyDefinition.set = function proxySetter (val) {
    6.     this[sourceKey][key] = val;
    7.   };
    8.   Object.defineProperty(target, key, sharedPropertyDefinition);
    9. }
    1. /**
    2.  * Define a reactive property on an Object.
    3.  */
    4. function defineReactive$$1 (
    5.   obj,
    6.   key,
    7.   val,
    8.   customSetter,
    9.   shallow
    10. ) {
    11.   var dep = new Dep();
    13.   var property = Object.getOwnPropertyDescriptor(obj, key);
    14.   if (property && property.configurable === false) {
    15.     return
    16.   }
    18.   // cater for pre-defined getter/setters
    19.   var getter = property && property.get;
    20.   var setter = property && property.set;
    21.   if ((!getter || setter) && arguments.length === 2) {
    22.     val = obj[key];
    23.   }
    25.   var childOb = !shallow && observe(val);
    26.   Object.defineProperty(obj, key, {
    27.     enumerable: true,
    28.     configurable: true,
    29.     get: function reactiveGetter () {
    30.       var value = getter ? getter.call(obj) : val;
    31.       if (Dep.target) {
    32.         dep.depend();
    33.         if (childOb) {
    34.           childOb.dep.depend();
    35.           if (Array.isArray(value)) {
    36.             dependArray(value);
    37.           }
    38.         }
    39.       }
    40.       return value
    41.     },
    42.     set: function reactiveSetter (newVal) {
    43.       var value = getter ? getter.call(obj) : val; // <==
    44.       /* eslint-disable no-self-compare */
    45.       if (newVal === value || (newVal !== newVal && value !== value)) {
    46.         return
    47.       }
    48.       /* eslint-enable no-self-compare */
    49.       if (process.env.NODE_ENV !== 'production' && customSetter) {
    50.         customSetter();
    51.       }
    52.       // #7981: for accessor properties without setter
    53.       if (getter && !setter) { return }
    54.       if (setter) {
    55.         setter.call(obj, newVal);
    56.       } else {
    57.         val = newVal;
    58.       }
    59.       childOb = !shallow && observe(newVal);
    60.       dep.notify();
    61.     }
    62.   });
    63. }