I am working on a framework project where I have a sub class implemented from base class. When I prepare build I am just making sub class public but not the base class which results the following lexical error:
Lexical or Preprocessor Issue Group
But if I make the base class also public then it is okay. But I don't want to expose base class to the outer world. I mean don't want to make base class public.
Here is definition of base class
#interface BaseClass : NSObject
- (void)baseFunction;
#end
definition of sub class:
#interface SubClass : BaseClass
- (void)subFunction;
#end
and the header file:
#import <UIKit/UIKit.h>
#import <FileUtil/SubClass.h>
Please let me know how I can overcome the situation. Thanks in advance :)
You need to add this function declaration in #implementation file with Extension so it will hide from other user who will use your framework.
BaseClass.h
#interface BaseClass : NSObject
#end
BaseClass.m
#interface BaseClass ()
//its private method for out side class
- (void)baseFunction;
#end
#implementation BUViewController
#end
How by this example you can get some idea how to make private method to hide from others.
Related
What's the difference between declaring a #private ivar in the header file and declaring the same ivar in the class extension without #private? As far as I understand it's the same thing.
Also, can you declare a private property in the header?
The concept is to declare in the header file only those things (methods, properties, etc) which are public. Declare all private items in the implementation file's class extension.
This provides the class users only information that is available for their use and hides all else. It also make it easier for a user of the class quickly see the functionality available to him. Writing code is all about readability and understandability to the developer.
This way a developer is free to change anything that is not exposed in the header files without making any externally visible changes.
In recent versions of Objective this is finally fully releasable via class extensions.
What's the difference between declaring a #private ivar in the header file and declaring the same ivar in the class extension without #private?
There are a few differences. In short, variables declared in the header file are visible to subclasses and class categories. Variables declared in the implementation are not.
1) Instance variables declared in a class's main #interface block are available to external class categories or extensions, even if those variables are declared #private. E.g.:
// YourClass.h
#interface YourClass : NSObject {
#private
int _yourPrivateIVar;
}
#end
// MyExtension.m
#implementation YourClass(MyExtension)
- (void)reset { _yourPrivateIVar = 0; } // This is allowed.
#end
Instance variables declared in the implementation are not available to external class categories.
2) A base class and its subclass cannot both declare the same ivar in their #interface, even if both ivars are #private. E.g., this is not allowed:
#interface Base : NSObject
{
#private
int _foo;
}
#end
#interface Subclass : Base
{
#private
int _foo; // Error: Duplicate member _foo
}
#end
If both ivars are declared in a class extension or implementation block then not only does it compile but it works as expected: both classes have their own separate _foo ivars that do not conflict with one another. On other words, both variables are truly private and separate:
#implementation Base {
int _foo;
}
#end
#implementation Subclass {
int _foo;
}
- (void)reset { _foo = 123; } // Does not affect base class's _foo
#end
Note: If the base class and subclass declare a "private" property or method with the same name it will compile without warning or error, but it will fail spectacularly at runtime as both classes unknowingly interfere with each other's private data.
I've got a dylib framework with some UIView subclasses made in swift which I've done to use the new #IBDesignable and #IBInspectable stuff.
So lets say I've got a UITextField subclass in there named MyTextField.swift like this:
MyTextField.swift
#IBDesignable class MyTextField: UITextField {
// some properties etc.
// content is irrelevant
}
Now it compiles and works well in InterfaceBuilder so far so good. But what I need to do is import this special subclass into my Objective C implementation of the controller to set a property in code at runtime.
The framework (named myViews) has a header called myViews.h which I am able to import into the controllers header like this:
MyViewController.h:
#import myViews;
#import <UIKit/UIKit.h>
#import "myViews.h"
#interface MyViewController : UIViewController
#property(weak, nonatomic) IBOutlet MyTextField *txtName; // <-- This is the problem!
#end
This is where I'm stuck! So the class MyTextField is unknown from the imported headers. The myViews.h was automatically generated. I've tried to import the bridging-headers in there without success.
myViews.h:
#import <UIKit/UIKit.h>
//! Project version number for myViews.
FOUNDATION_EXPORT double myViewsVersionNumber;
//! Project version string for myViews.
FOUNDATION_EXPORT const unsigned char myViewsVersionString[];
// In this header, you should import all the public headers of your framework
// using statements like #import <myViews/PublicHeader.h>
#import <myViews/MyTextField-Swift.h> // <-- This is what I've tried to import here which doesn't work as well.
Hope anybody may help me out. Thanks in advance.
In your objective-c class, try importing your swift module like this:
#import "<ModuleName>-Swift.h"
Where ModuleName is the name of the module containing the swift code
I want to have a variable that will only be visible to its subclasses which is exactly similar to what protected variables are in Java.
I tried like this on the parent's implementation file
#interface ParentClass (){
NSArray *_protectedVar
}
but unfortunately the protectedVar is not visible as soon as I call super.protectedVar
Correct my if I am wrong but I don't wanna use #properties to that variable since it will make that variable public.
And this is my subclass's header file looks like #interface SubClass : ParentClass
The code you posted declares an instance variable in an Objective-C class extension, and therefore the variable's default visibility is private. You can use a visibility modifier to change the ivar's visibility, as shown below:
#interface ParentClass ()
{
#protected
NSArray *_protectedVar
}
If you have this
ParentClass.h
#interface ParentClass : NSObject{
NSArray *_protectedVar
}
Then just like how you access normal ivar, use _protectedVar directly.
But I suggest you use property with private header
Parent.h
#interface Parent : NSObject
#property id publicProperty;
#end
Parent_Protected.h
#interface Parent (Protected)
#property id protectedProperty
#end
So normal class only #import "Parent.h", they can't see protected property.
But subclass can #import "Parent_Protected.h" and use protected property with self.protectedProperty
I am trying to inherit from MKPinAnnotation in this manner:
MKPinAnnotationView -->MyPoint-->PhotoPoint
but I get an error in Xcode saying PhotoPoint can't be defined without a base class.
Here is my code in MyPoint.h:
#import <MapKit/MKPinAnnotationView.h>
#interface MyPoint:NSObject<MKAnnotation>{...}
then in PhotoPoint.h:
#interface PhotoPoint:MyPoint
and this is where I get the error...does anyone have any ideas?
In PhotoPoint.h you need to import MyPoint.h.
#import "MyPoint.h"
#interface PhotoPoint : MyPoint
This question already has answers here:
Why is there another #interface inside the.m file? [duplicate]
(6 answers)
Closed 9 years ago.
As we know, normally we used to declare our class instance variables, properties, method declarations in class header file (.h).
But we can do the same things, in .m file, using blank category.
So my question is: what should be declared in .h file and what should be declared in .m file - and why?
Regards,
Mrunal
New Edit:
Hi all,
If you refer to newly added Apple examples over developer.apple.com - they are now declaring their IBOutlets and IBActions in .m file itself and that too with property declaration. But we can achieve the same thing by declaring those references in .h file in class private member section.
Then why are they declaring those in .m file and as properties, any idea?
-Mrunal
But we can do the same things, in .m file, using blank category.
A class continuation.
Normally, you choose to declare something in the header if it is intended to be public -- used by any client. Everything else (your internals) should typically go in the class continuation.
I favor encapsulation -- Here's my approach:
variables
Belongs in the class continuation or #implementation. Exceptions are very, very rare.
properties
Typically belongs in the class continuation in practice. If you want to give subclasses the ability to override these or to make these part of the public interface, then you could declare them in the class declaration (the header file).
method declarations
More in the class continuation than in the class declaration. Again, if it is meant to be used by any client it would belong in the class declaration. Often, you won't even need a declaration in the class continuation (or class declaration) -- the definition alone is adequate if it is private.
Basically, in the header file (.h) you declare your public API, while in the implementation file (.m) you declare your private API.
Visibility in Objective-C
You can also find the answer here
It's mostly up to you.
The .h file is like the description of your class.
It's smart to only put in the .h file what's really important to be visible from the outside of the class, especially if you're working with other developers.
It will help them to understand more easily what methods/properties/variables they can use, rather than having a whole list of things they don't.
Usually you want to use blank category in .m file for declaration of private properties.
// APXCustomButton.m file
#interface APXCustomButton ()
#property (nonatomic, strong) UIColor *stateBackgroundColor;
#end
// Use the property in implementation (the same .m file)
#implementation APXCustomButton
- (void)setStyle:(APXButtonStyle)aStyle
{
UIColor *theStyleColor = ...;
self.stateBackgroundColor = theStyleColor;
}
#end
If you try to access property declared in black category outside .m file, you will receive undeclared property compiler error:
- (void)createButton
{
APXCustomButton *theCustomButton = [[APXCustomButton alloc] init];
theCustomButton.stateBackgroundColor = [UIColor greenColor]; // undeclared property error
}
In most cases, if you want add new method/properties to an existing class without subclassing, then you want declare category in .h file and implementation of declared methods in .m file
// APXSafeArray.h file
#interface NSArray (APXSafeArray)
- (id)com_APX_objectAtIndex:(NSInteger)anIndex;
#end
// APXSafeArray.m file
#implementation NSArray
- (id)com_APX_objectAtIndex:(NSInteger)anIndex
{
id theResultObject = nil;
if ((anIndex >= 0) && (anIndex < [self count]))
{
theResultObject = [self objectAtIndex:anIndex];
}
return theResultObject;
}
#end
Now you can use "com_APX_objectAtIndex:" method wherever "APXSafeArray.h" is imported.
#import "APXSafeArray.h"
...
#property (nonatomic, strong) APXSafeArray *entities;
- (void)didRequestEntityAtIndex:(NSInteger)anIndex
{
APXEntity *theREquestedEntity = [self.entities com_APX_objectAtIndex:anIndex];
...
}