Create a compiler error when a variable is nil - ios

Question

I need to trigger a custom compiler error when the developer forgot to enter a key in LocalizedStrings, in order to alert him this would cause the app will show the key instead the text. Personally I think that's perfect, but I have been required to launch a compiler error because the app has to many cases and to protect the developer in case of absentmindedness.
The method inside which is suppose to receive the key, would be something like:
- (NSString *) localizedString:(NSString *)key {
HERE IS WHERE I WANT TO TRHROW THE COMPILER ERROR
}

Answer 1

If you want a compile time error, look into annotating the argument with _Nonnull:
-(NSString *)localizedString:(NSString * _Nonnull)key
...and turning on the -Wnullable-to-nonnull-conversion warning with -Werror to turn this into an error. The main problem to deal with here is going to be the masses of existing code that will now fail because of nullable-to-nonnull conversions elsewhere, requiring a proliferation of annotations throughout your source code. This probably isn't going to be a workable solution but you can investigate it at least.
If you want a runtime error in debug mode only, use NSAssert or NSParameterAssert:
NSParameterAssert(key != nil);
// OR:
NSAssert(key != nil, "key must be non-nil");
// or just
NSAssert(key, "key must be non-nil");
If you always want a runtime error, throw an exception either with #throw or the convenience method:
if (!key) {
[NSException raise:#"MyException" format:#"key must be non-nil"];
}

Answer 2

You can use in this way.
-(NSString *) localizedString:(NSString *)key
{
if (key == nil || key == (id)[NSNull null])
{
NSException* myException = [NSException
exceptionWithName:#"NullException"
reason:#"You have passed null value in key"
userInfo:nil];
#throw myException;
}
else
{
}
}

Answer 3

There are two things here.
1. Compile time error
2. Run time error
Your build will succeed as there is no problem with the syntax. Hence there can be no compile time error here.
What you actually need is a mechanism to fail the build when the app is about to be built.
This can be achieved by using build phases.
Go to build phases. Add your script which would look for keys in your code and check for the same key in your .string files. Essentially, you'll not initailize the building process when your script fails