How to retrieve Userdefault in objectiveC class from Swift class?

Question

I have saved userdefault string value in swift class and How to retrieve that value in Objective C class? I have used https://stackoverflow.com/questions/44171504/userdefaults-between-objective-c-and-swift this it is working from Objc to swift but not vice-versa.

EXAMPLE CODE

Saved in ObjC class

[[NSUserDefaults standardUserDefaults] setObject:@"HELLO" forKey:@"kcString"];

Retrieved in Swift class using

if let str = UserDefaults.standard.string(forKey: "kcString") {
    print("Found kcString \(str)")
} else {
    print("No string for key kcString")
}

but not working in reverse way.

Saved in swift class using :

UserDefaults.standard.set("hello", forKey: "kcString")

Tried to retrieve in objc class using:

self.val = [[NSUserDefaults standardUserDefaults] stringForKey:@"kcString"];

What do you mean by "not working"? Could you provide the code for the "vise-versa"? — Ahmad F, Aug 01 '18 at 07:40

score 1 · Accepted Answer · answered Aug 01 '18 at 08:56

As the user defaults are associated with you application not with any file. You can access the user default with any kind of file whether it is in swift or in objective c. I am assuming you are working with single target. Please follow the concept.

I have made a swift project. I have added an objective c file. I have also added the bridging header file. Now i will access the user default values as:

In .h file describe two methods as:

@interface UDF_Objc_Access : NSObject

    +(void)set_udf_value_objc:(NSString *)value for:(NSString*)key;
    +(NSString *)get_udf_swift_value_for:(NSString*)key;

@end

In .m implementation file give the definition as:

@implementation UDF_Objc_Access

+(void)set_udf_value_objc:(NSString *)value for:(NSString *)key {
    [[NSUserDefaults standardUserDefaults] setObject:value forKey:key];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

+(NSString *)get_udf_swift_value_for:(NSString *)key {
    return [[NSUserDefaults standardUserDefaults] stringForKey:key];
}

@end

Now in your Appdelegate.swift do:

     /*
     key names
     swift key = "swift_key"
     objective c key = "objc_key"
     */
    let swift_key = "swift_key"
    let objc_key = "objc_key"


    //MARK:- Case 1
    /*
     Save value from swift file & get it from objective c file
     */

    UserDefaults.standard.set("This value is saved from swift class", forKey: swift_key)
    UserDefaults.standard.synchronize()

    //getting value from objective c class
    print(UDF_Objc_Access.get_udf_swift_value_(for: swift_key))

    /*
     Set value from objective c file & get it with swift
     */
    UDF_Objc_Access.set_udf_value_objc("This value is saved from objective c file", for: objc_key)

    //print value form swift
    print(UserDefaults.standard.value(forKey: objc_key)!)

Note: If you are working with multiple targets then use the app groups.

Yeah you are correct Thanks. It doesn't work for the same key. — Shrava giri, Aug 01 '18 at 09:03
Don't use `.synchronize()`. From [Apple's documentation](https://developer.apple.com/documentation/foundation/nsuserdefaults/1414005-synchronize?language=swift) _"this method is unnecessary and shouldn't be used."_ — Ashley Mills, Oct 11 '18 at 14:21

How to retrieve Userdefault in objectiveC class from Swift class?

1 Answers1