What is the correct way of init iVar variables in

问题:

Example iVar foo,

@property (nonatomic) NSString* foo; // inside .h

Option 1

@Synthesize foo; //Inside .m 

foo = [[NSString alloc] init]; // viewDidLoad method

Option 2

@Synthesize foo; //Inside .m 

self.foo = [[NSString alloc] init]; // viewDidLoad method

Option 3

@Synthesize foo = _foo; //Inside .m 

_foo = [[NSString alloc] init]; // viewDidLoad method

Why?

At so many places I have seen code which has different ways of doing init an Object in Obj - C but which one is the best practise?

回答1:

In this regard, ARC is the same as MRC.

you have specified all these take place in viewDidLoad. in that case, use the setter (Option 2).

if you were to initialize/set in the initializer, then you would use direct access. the basic reason is that in the initializer (e.g. -init), you have a partially initialized object. during initialization, you want to focus on initializing variables your class needs or expects in order to function correctly. as well, you want to avoid side-effects you can encounter when using the accessors in partially constructed states.

in a fully constructed state (e.g. viewDidLoad), you should relegate the implementation to the accessors for correct behavior, as specified by your object's interface.

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Additional Reading:

Initializing a property, dot notation

Should I refer to self.property in the init method with ARC?

Why would you use an ivar?

回答2:

I think you should understand the difference between these three and then decide which one is good for you.

option 1: Here while initializing you are not using the synthesizer method. so there is no use of declaring property-synthesizer in .h and .m

option 2: here you are using property-synthesizer. But the name of the method for accessing the instance and actual instance variable is same.

option 3: Here again you are not using the property-synthesizer method. Here foo is the name of the method and _foo is the actual instance.

In my opinion third one is the good. Since you the difference you can decide which one is good for you.