Convert all values of Container into NSString - ios

Question

I have a problem to communicate with a server. The webserver expects all parameters in the JSON object to be a string. So every number and every boolean in every container needs to be a string.
For my example I have a NSDictionary full of key values (values are all kinds of types - numbers, arrays etc.). For example:
{
"AnExampleNumber":7e062fa,
"AnExampleBoolean":0,
"AnExampleArrayOfNumber":[17,4,8]
}
Has to become:
{
"AnExampleNumber":"7e062fa",
"AnExampleBoolean":"0",
"AnExampleArrayOfNumber":["17","4","8"]
}
I tried the standard NSJSONSerializer but it doesn't give me any option to do what I need. I then tried to transform everything in the dictionary manually to be a string but that seems to be overhead. Does anyone have hint for me? Maybe a serializer that does just that or a function to convert any objects in a container to strings?

Answer 1

This is one way you could do it. It's non-optimized and has no error handling. It only supports the kinds of objects that NSJSONSerializer supports.
#import <Foundation/Foundation.h>
#interface NSObject(SPWKStringify)
- (id)spwk_stringify;
#end
#implementation NSObject(SPWKStringify)
- (id)spwk_stringify
{
if ([self isKindOfClass:[NSDictionary class]]) {
NSDictionary *dict = (NSDictionary *)self;
NSMutableDictionary *newDict = [[NSMutableDictionary alloc] init];
for (NSString *key in [dict allKeys]) {
newDict[key] = [dict[key] spwk_stringify];
}
return newDict;
} else if ([self isKindOfClass:[NSArray class]]) {
NSMutableArray *newArray = [[NSMutableArray alloc] init];
for (id value in ((NSArray *)self)) {
[newArray addObject:[value spwk_stringify]];
}
return newArray;
} else if (self == [NSNull null]) {
return #"null"; // representing null as a string doesn't make much sense
} else if ([self isKindOfClass:[NSString class]]) {
return self;
} else if ([self isKindOfClass:[NSNumber class]]) {
return [((NSNumber *)self) stringValue];
}
return nil;
}
#end
int main(int argc, char *argv[]) {
#autoreleasepool {
NSDictionary *dict = #{
#"AnExampleNumber": #1234567,
#"AnExampleBoolean": #NO,
#"AnExampleNull": [NSNull null],
#"AnExampleArrayOfNumber": #[#17, #4, #8],
#"AnExampleDictionary": #{#"innerKey": #[#55, #{#"anotherDict": #[#"foo", #[#1, #2, #"three"]]}]}
};
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:[dict spwk_stringify] options:NSJSONWritingPrettyPrinted error:NULL];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
NSLog(#"result: %#", jsonString);
}
}
The output will be:
result: {
"AnExampleNumber" : "1234567",
"AnExampleNull" : "null",
"AnExampleDictionary" : {
"innerKey" : [
"55",
{
"anotherDict" : [
"foo",
[
"1",
"2",
"three"
]
]
}
]
},
"AnExampleBoolean" : "0",
"AnExampleArrayOfNumber" : [
"17",
"4",
"8"
]
}
Note: Please keep in mind that turning [NSNull null] into a string doesn't make any sense and might actually be misleading and dangerous.
Enjoy.

Answer 2

(I assume you mean NSJSONSerializer, not NSSerializer.)
I doubt you'll find a pre-rolled solution to this. It's not a general problem. As you note, this is incorrect JSON, so JSON serializers shouldn't do it.
The best solution IMO is just write the code to transform your NSDictionary into another NSDictionary that is in the form you want. If you really want to make it a generic solution, I suspect that a custom NSDictionary walker with isKindOfClass: is your best bet. Something like this should work:
NSDictionary *myStringDictForDict(NSDictionary *dict); // forward decl if needed
NSArray *myStringArrayForArray(NSArray *array) {
NSMutableArray *result = [NSMutableArray new];
[array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj isKindOfClass:[NSArray class]]) {
[result addObject:myStringArrayForArray(obj)];
} else if ([obj isKindOfClass:[NSDictionary class]]) {
[result addObject:myStringDictForDict(obj)];
} else {
[result addObject:[obj description]];
}
}];
return result;
}
NSDictionary *myStringDictForDict(NSDictionary *dict) {
NSMutableDictionary *result = [NSMutableDictionary new];
[dict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
if ([obj isKindOfClass:[NSArray class]]) {
result[key] = myStringArrayForArray(obj);
} else if ([obj isKindOfClass:[NSDictionary class]]) {
result[key] = myStringDictForDict(obj);
} else {
result[key] = [obj description];
}
}];
return result;
}