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How to set the current value of UITextField to a property(through a custom setter) declared in category which extends UITextField class when firing editingDidBegin control event of UITextField?

Rakesha Shastri
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PSkyMax
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  • Explain your question briefly. – Mathi Arasan Aug 13 '18 at 09:06
  • I want to get the current value of UITextField to a variable when "UIControlEventEditingDidBegin" control event fires. I also want to add this behavour to all of my UITextField objects to check whether textfield value is edited or not. So I created a category which extends UITextField class and add a public property to store the value and now I want to set the textfield's value to this property when "UIControlEventEditingDidBegin" UITextcField's control event fires . Thanks ... – PSkyMax Aug 13 '18 at 09:49

1 Answers1

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You should be able to do this using a category by taking advantage of Associative References.

From the docs:

Using associative references, you can add storage to an object without modifying the class declaration.

Here's an example that will get you going in the right direction:

.h file: 

@interface UITextField (StoredProperty)

@property (nonatomic, strong) NSString *testString;

@end

.m file: 

#import <objc/runtime.h>

static void *MyStoredPropertyKey = &MyStoredPropertyKey;

@implementation UITextField (StoredProperty)

- (NSString *)testString {
    return objc_getAssociatedObject(self, MyStoredPropertyKey);
}

- (void)setTestString:(NSString *)testString {
    objc_setAssociatedObject(self, MyStoredPropertyKey, testString, OBJC_ASSOCIATION_RETAIN_NONATOMIC); 
}

@end

Example use: 

NSObject *obj = [NSObject new];
obj.testString = @"This is my test string";
NSLog(@"%@", obj.testString);
tww0003
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  • Thanks @ tww0003 for your answer. I also followed associative references. But how to set the UITextField's value to "testString" property when "UIControlEventEditingDidBegin" control event fire? – PSkyMax Aug 14 '18 at 03:55
  • @PSkyMax You could create another category, but this time for UITextFieldDelegate and set it in the `textFieldDidBeginEditing:` method. Hope this helped, and if it did don't forget to mark the answer as accepted! Here's the relevant documentation: https://developer.apple.com/documentation/uikit/uitextfielddelegate/1619590-textfielddidbeginediting?language=objc – tww0003 Aug 14 '18 at 14:22