Objective C: Calling instance method from class method

Question

this is the problem:

myObject.h

@interface myObject
- (void) Init;
- (void) doStuffs;
- (void) Final;
+ (NSData*) staticMethod: (NSString*) filePath
@end

myObject.m

@implementation myObject

- (void) Init {
...
}

- (void) doStuffs {
...
}

- (void) Final {
...
}

+ (NSData*) staticMethod: (NSString*) filePath {
    myObject *objInstance;

    [objInstance Init];
    [objInstance doStuffs];
    [objInstance Final];
}
@end

When calling Init, doStuffs and Final on the static method, the instance methods are not called; any idea?

For short: I need to call instance method from a static method of the same class...

Thank you for helping.

alloc/init of objInstance isn't done.

Larme
– Larme

2016-03-23 18:25:27 +00:00
Commented Mar 23, 2016 at 18:25 — Larme
– Larme, Commented Mar 23, 2016 at 18:25

Tommy · Accepted Answer · 2016-03-23 18:24:41Z

4

You haven't created an instance of myObject. So, assuming ARC, you're calling on nil. Calling on nil doesn't do anything.

So:

myObject *objInstance = [[myObject alloc] init];

answered Mar 23, 2016 at 18:24

Tommy

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Comments

Mark · Accepted Answer · 2016-03-23 21:27:41Z

1

If you don't initialize objInstance, it'll be nil and those calls won't do anything. Allocate and initialize objInstance first. You can also check objInstance for nil before calling those methods and you'll see it is nil.

This is one of the trickier things about Objective-C. Java would throw a NullPointerException if you tried something like this. Objective-C silently keeps chugging along!

edited Mar 23, 2016 at 21:27

answered Mar 23, 2016 at 18:25

Mark

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