mobx動態添加observable

mobx使用extendObservable來動態添加observable屬性。

extendObservable(target, properties, decorators?, options?)

例如：

var Person = function(firstName, lastName) {
    // 在一個新實例上初始化 observable 屬性
    extendObservable(this, {
        firstName: firstName,
        lastName: lastName,
        get fullName() {
            return this.firstName + " " + this.lastName
        },
        setFirstName(firstName) {
            this.firstName = firstName
        }
    }, {
        setFirstName: action
    });
}

var matthew = new Person("Matthew", "Henry");

// 向 observable 對象添加 observable 屬性
extendObservable(matthew, {
    age: 353
});

observable.object(object) 實際上是 extendObservable({}, object) 的別名