Creating Dictionary from a model that contains nil values - objective-c

Question

I have the following Model:
#interface Person : NSObject
#property (nonatomic, copy) NSString *firstName;
#property (nonatomic, copy) NSString *middleName;
#property (nonatomic, copy) NSString *lastName;
#property (nonatomic, copy) NSString *status;
#property (nonatomic, copy) NSString *favoriteMeal;
#property (nonatomic, copy) NSString *favoriteDrink;
#property (nonatomic, copy) NSString *favoriteShow;
#property (nonatomic, copy) NSString *favoriteMovie;
#property (nonatomic, copy) NSString *favoriteSport;
-(NSDictionary *)getSomeInfo;
-(NSDictionary *)getAllInfo;
#end
Part 1:
I want getSomeInfo to return NSDictionary (e.g. {"firstName", self.firstName}) for all the fields that does not contain nil. How can I do that? (I could check every value but I wonder if there's a better way)
Part 2:
I want getAllInfo to return NSDictionary with all the property and if one contains nil then it should throw an error. Again do I have to write a long conditional statement to check or is there a better way?
Note: I want to do this without using external library. I'm new to the language so I'm open to suggestions if there's a better pattern in Objective-C.

Answer 1

There are two approaches.
1) Check each value:
- (NSDictionary *)getSomeInfo {
NSMutableDictionary *res = [NSMutableDictionary dictionary];
if (self.firstName.length) {
res[#"firstName"] = self.firstName;
}
if (self.middleName.length) {
res[#"middleName"] = self.middleName;
}
// Repeat for all of the properties
return res;
}
2) Use KVC (Key-value coding):
- (NSDictionary *)getSomeInfo {
NSMutableDictionary *res = [NSMutableDictionary dictionary];
NSArray *properties = #[ #"firstName", #"middleName", #"lastName", ... ]; // list all of the properties
for (NSString *property in properties) {
NSString *value = [self valueForKey:property];
if (value.length) {
res[property] = value;
}
}
return res;
}
For the getAllInfo method you can do the same but instead return nil if any value is missing. Treat the nil results as your indication that not all properties have a value.