CODEWITHSUNDEEP
iphoneobjective-ccocoa
user310291
user310291

Reputation: 38220

How to do lazy instantiation in objective c?

In one of the Standford IOS tutorials, the instructor uses lazy instantiation for creating an instance of calculator engine class.

He uses the second syntax exposed in my former question:

@synthesize myTextField = _myTextField;

In this syntax the getter myTextField has different name from _myTextField so it is possible to test

if (_myTextField != nil) { ... }

How do I do this with classical first syntax, since the getter and instance variable name are the same (myTextField)?

Upvotes: 3

Views: 2371

Answers (1)

wattson12
wattson12

Reputation: 11174

if you use @sythensize variableName = _variableName; then the instance variable will be called _variableName and that is what you need to use to access it directly. variableName is the name which will be used to generate setters and getters, so self.variableName or [self setVariableName:...]

if you use @synthesize variableName; then the instance variable will have the same name as the synthesised setters and getters. You can still access the instance variable with variableName = ... but its easier to get mixed up which one you should be using

so 2 lazy loading implemetations

@synthesize varName = _varName

- (id)varName
{
    if (!_varName)
        _varName = [[NSObject alloc] init];

    return _varName;
}

or

@synthesize varName;

- (id)varName
{
    if (!varName)
        varName = [[NSObject alloc] init];

    return varName;
}

Personally, I go for @synthesize varName = _varName its much easier to read and harder to mix up when you're accessing the variable when you meant the setter and vice versa

Upvotes: 4

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