ios - Why do some books say that the initialization method and dealloc method should always read and write data through instance variables?
我想大声告诉你2017-05-17 10:05:31
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Effiective objecttive -c2.0 This book says that the initialization method and dealloc method should always read and write data through instance variables. After reading it for a long time, I didn’t understand the reason? Has anyone read this book?
_name = @"Jack" It is fast to directly assign values to variables without sending messages through setters.
For the following name attributes:
@property (nonatomic, copy) NSString *name;
Direct assignment is: _name = @"Jack"; ，通过 self.name = @"Jack" 其实等同于 _name = @"Jack".copy;
self.name = @"Jack" 会触发KVO，_name = @"Jack" will trigger KVO,
will not
self.name = @"Jack"
You can perform breakpoint debugging in the setter method, and you will know every assignment.
NSString *str = _name,赋值用 self.name = @"Jack"So there is a reasonable compromise solution, which is to use NSString *str = _name when reading data, and use
when assigning values.
self.name = @"Jack"可能不等同于 _name = @"Jack".copyAnother thing to note is that subclasses may override setter methods, and using
may not be equivalent to _name = @"Jack".copy.
I don’t understand what you are unclear about, so I can only briefly describe it using my ideas. 🎜
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Isn’t it very clear in the book:
_name = @"Jack"It is fast to directly assign values to variables without sending messages through setters.For the following
nameattributes:Direct assignment is:
_name = @"Jack";，通过self.name = @"Jack"其实等同于_name = @"Jack".copy;
will notself.name = @"Jack"会触发KVO，_name = @"Jack"will trigger KVO,
You can perform breakpoint debugging in the setter method, and you will know every assignment.self.name = @"Jack"
when assigning values.NSString *str = _name,赋值用self.name = @"Jack"So there is a reasonable compromise solution, which is to useNSString *str = _namewhen reading data, and use
may not be equivalent toself.name = @"Jack"可能不等同于_name = @"Jack".copyAnother thing to note is that subclasses may override setter methods, and using_name = @"Jack".copy.
I don’t understand what you are unclear about, so I can only briefly describe it using my ideas. 🎜