convert NSTaggedPointerString to NSString

NSTaggedPointerString is already an NSString, it's just a subclass. You can use it anywhere you can use an NSString, without conversion.

I had this same issue multiple times. It would seem that type inference for NSDictionary is not an exact science. What I do is specifically ask if the object responds to a particular method. For example if I am looping through parsing some JSON and I am attempting to access a value of type NSString:

NSString * string;
if ([[dict objectForKey:@"value"] respondsToSelector:@selector(stringValue)]) {
    string = [[dict objectForKey:@"value"] stringValue];
}
else {
   string = [NSString stringWithString:[dict objectForKey:@"value"]];
}
documentFile.documentRevision = string;

I have encountered places where NSTaggedPointerString cannot be used as a NSString, such as when creating an NSDictionary. In those cases use stringWithString::

NSString* <# myNSString #> = [NSString stringWithString:<# myNSTaggegedString #>];