关于使用 ivar 变量而不是 getters 的好处
虽然我使用 Objective-C 语法，但问题语言不可知。
假设以下声明
@synthesize activities = _activities;
self.activities 将调用 getter，并且 _activities 将检查为已分配的值。据我了解，此分配的主要好处是可以清楚地区分何时调用 setter 以及何时调用局部变量。
虽然这很好，但是使用 ivar 与使用 getter 方法相比，真正有形的好处是什么？
我能想到一个，其他的还有什么？
- 我认为使用 ivar 比调用 getter 更快，但与触摸事件相比，差异可以忽略不计。
Though i am using Objective-C syntax, the question language agnostic.
Assuming the following declaration
@synthesize activities = _activities;
self.activities will call the getter and _activities will check for the value which was already assigned. The main benefit of this assignment, as i understand it, is to clearly differentiate when setter is called and when local variables is called instead.
While this is nice, what is the real tangible benefit of using ivar vs using getter methods?
I can think of one, what are others?
- I suppose using ivar is faster then calling the getter, but compared with what goes on with touch events, the difference is negligible.
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直接访问实例变量意味着绕过合成访问器提供的任何原子性保护和内存管理。如果您在执行此操作时很清楚，则可以更轻松地审核此类访问，以确保您自己负责类行为的这些方面。
Accessing the instance variables directly means circumventing any atomicity protection and memory management supplied by the synthesized accessors. If it's clear when you're doing that, it's easier to audit such access to ensure that you're looking after these aspects of the class's behaviour yourself.