I need to check the type of each element in an array...
for(id obj in items) {
if([obj isKindOfClass:[NSString class]]) {
//handle string case
} else if([obj isKindOfClass:[NSInteger class]]) { //THIS LINE GIVES ERROR
//handle int case
}
}
Of course NSInteger is just an alias for int, so how can I check for this at runtime?
You can't actually store NSInteger in an NSArray, since it isn't an object. If you are storing numbers in your array, they are most likely instances of NSNumber, so you would check for:
if ([obj isKindOfClass:[NSNumber class]]) { ... }
iPhone Developer Tips gives a good summary of the difference between NSInteger and NSNumber.
Related
Everything works when i get more then 1 objects back but when its only 1 it reacts weird, i can't find the solution for it.
First i set everything in an array:
NSArray *array = [[[dictionary objectForKey:#"Response"] objectForKey:#"objecten"] objectForKey:#"object"];
if (array == nil) {
NSLog(#"Expected 'results' array");
return;
}
then i use a for loop on a dictionary
for (NSDictionary *resultDict in array) {
SearchResult *searchResult;
NSString *wrapperType = [resultDict objectForKey:#"type"];
if ([wrapperType isEqualToString:#"rent"])
{
searchResult = [self parseHuur:resultDict];
}
if (searchResult != nil) {
[searchResults addObject:searchResult];
}}
So when results get back more then 1 everything works great, but when just one gets back i get:
-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0x6e52c30
*** Terminating app due to uncaught exception
'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]:
unrecognized selector sent to instance 0x6e52c30'
it points to this line:
NSString *wrapperType = [resultDict objectForKey:#"type"];
I really don't get it...
i check the results of the api in the browser with the same link and it really returns 1 object, but when i log the resultDict (NSlog it) i get only one answer: id instead of the whole object with all parameters (i don't know if this is the right name for it)
how can that be ?
Some of your results aren't full NSDictionaries but rather just NSStrings. You can check for this:
for (id result in array) {
if ([result isKindOfClass:[NSDictionary class]]) {
NSDictionary *resultDict = (NSDictionary *)result;
...
As per your comments, array is not always an array as you have mentioned. It could be an array or dictionary. So try this,
id someObject = [[[dictionary objectForKey:#"Response"] objectForKey:#"objecten"] objectForKey:#"object"]; //naming it as someObject since it is not always an array
if (someObject == nil) {
NSLog(#"Expected 'results' array");
return;
}
if ([someObject isKindOfClass:[NSDictionary class]]) { //Just add this
someObject = [NSArray arrayWithObject:someObject];
}
NSArray *array = (NSArray *)someObject;//type cast to an array now
for (NSDictionary *resultDict in array) {
SearchResult *searchResult;
NSString *wrapperType = [resultDict objectForKey:#"type"];
if ([wrapperType isEqualToString:#"rent"])
{
searchResult = [self parseHuur:resultDict];
}
if (searchResult != nil) {
[searchResults addObject:searchResult];
}
}
When you use the fast enumeration for a NSDictionary, the iterating variable is from the set of keys in the dictionary not the values.
http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/objectivec/Chapters/ocFastEnumeration.html
The resultDict isn't an NSDictionary hence you can't invoke objectForKey: on this object.
A better solution would be to treat resultDict as id type in the for loop, and check its class type for NSDictionary before using it.
-[__NSCFString objectForKey:]
So it's calling the objectForKey: method on an NSString. It seems that the API you're using for getting the objects follows a common idiom: it uses duck-typing/polimorphism (to use these nice OO-related words) and it returns either an array of objects if it has more than results, or a single object (and not an array of one element) when it has only one result. So, you have to use reflection (OMG, even more OO terminology!) to inspect whether the returned object is actually an array - either
id result = [dictionary objectForKey:#"Response"];
id value;
if ([result isKindOfClass:[NSDictionary class]]) {
value = [[result object objectForKey:#"objecten"] objectForKey:#"object"];
} else {
value = result;
}
or
id value;
if ([dictionary isKindOfClass:[NSDictionary class]]) {
value = [[[dictionary objectForKey:#"Result"] result object objectForKey:#"objecten"] objectForKey:#"object"];
} else {
value = dictionary;
}
Try both, whichever works should be fine.
for (NSArray *values in [serializedJSON allValues])
Sometimes the values in serializedJSON will be arrays, and sometimes they will be NSDictionaries. I would like to discriminate against one of them so I don't get any errors like I am now. So I only want the returning values in this case to be NSArrays, while in a second case I would only want them to be NSDictionaries.
Thanks in advanced!
If you need more info let me know
The standard, generic way to handle JSON is roughly as follows:
NSObject* jsonResult = [serializedJSON allValues];
if ([jsonResult isKindOfClass:[NSArray class]]) {
<handle NSArray>
}
else if ([jsonResult isKindOfClass:[NSDictionary class]]) {
<handle NSDictionary>
}
else if ([jsonResult isKindOfClass:[NSNumber class]]) {
<handle NSNumber>
}
else if ([jsonResult isKindOfClass:[NSString class]]) {
<handle NSString>
}
else if (jsonResult == [NSNull null]) {
<handle null>
}
can anyone tell me please why returnSet is returning as nil when there are lowercase characters in 'program'
I have stepped through and the NSLog is definitely picking the variables out but when it addObject: it just doesn't?
+ (NSSet *)variablesUsedInProgram:(id)program
{
NSMutableSet *returnSet = [[NSMutableSet alloc]init];
if ([program isKindOfClass:[NSArray class]]) {
[program enumerateObjectsUsingBlock: ^(id obj, NSUInteger idx, BOOL *stop)
{
if ([obj isKindOfClass:[NSString class]]) {
if ([obj rangeOfCharacterFromSet:[NSCharacterSet lowercaseLetterCharacterSet]].location != NSNotFound) {
NSLog(#"Variable: %#", obj);
[returnSet addObject:obj];
}
}
}];
}
return returnSet;
}
The posted code has no bug. It cannot return a value of nil.
Your error is elsewhere.
I'm guessing that your problem is an ARC memory management problem. The code you posted returns a non-owning reference to the set it creates. Unless you save it to a strong instance variable, it will be deallocated.
For iOS, given some NSDictionary key/value pairs where strings values were added as NSString and int/float values were added as NSNumber, is there a way to test the data type of a value to see whether it is NSString or NSNumber?
NSObject offers:
- (BOOL)isKindOfClass:(Class)aClass
if obj is the value you get out of the NSDictionary then checkout:
[obj isKindOfClass:[NSString class]]
[obj isKindOfClass:[NSNumber class]]
If you check for these and you don't expect anything but NSString or NSNumber in the dictionary, then I would add an NSAssert in the else block.
There's more comments here on nuances of NSString and NSCFString:
In Objective-C, how do I test the object type?
Dictionary return an id you can check its class type as follows
if ([[dictionary valueForKey:#"key"] isKindOfClass:[NSString class]]) {
NSLog(#"it is a string");
}
else {
NSLog(#"it is number");
}
I'm setting values for properties of my NSManagedObject, these values are coming from a NSDictionary properly serialized from a JSON file. My problem is, that, when some value is [NSNull null], I can't assign directly to the property:
fight.winnerID = [dict objectForKey:#"winner"];
this throws a NSInvalidArgumentException
"winnerID"; desired type = NSString; given type = NSNull; value = <null>;
I could easily check the value for [NSNull null] and assign nil instead:
fight.winnerID = [dict objectForKey:#"winner"] == [NSNull null] ? nil : [dict objectForKey:#"winner"];
But I think this is not elegant and gets messy with lots of properties to set.
Also, this gets harder when dealing with NSNumber properties:
fight.round = [NSNumber numberWithUnsignedInteger:[[dict valueForKey:#"round"] unsignedIntegerValue]]
The NSInvalidArgumentException is now:
[NSNull unsignedIntegerValue]: unrecognized selector sent to instance
In this case I have to treat [dict valueForKey:#"round"] before making an NSUInteger value of it. And the one line solution is gone.
I tried making a #try #catch block, but as soon as the first value is caught, it jumps the whole #try block and the next properties are ignored.
Is there a better way to handle [NSNull null] or perhaps make this entirely different but easier?
It might be a little easier if you wrap this in a macro:
#define NULL_TO_NIL(obj) ({ __typeof__ (obj) __obj = (obj); __obj == [NSNull null] ? nil : obj; })
Then you can write things like
fight.winnerID = NULL_TO_NIL([dict objectForKey:#"winner"]);
Alternatively you can pre-process your dictionary and replace all NSNulls with nil before even trying to stuff it into your managed object.
Ok, I've just woke up this morning with a good solution. What about this:
Serialize the JSON using the option to receive Mutable Arrays and Dictionaries:
NSMutableDictionary *rootDict = [NSJSONSerialization JSONObjectWithData:_receivedData options:NSJSONReadingMutableContainers error:&error];
...
Get a set of keys that have [NSNull null] values from the leafDict:
NSSet *nullSet = [leafDict keysOfEntriesWithOptions:NSEnumerationConcurrent passingTest:^BOOL(id key, id obj, BOOL *stop) {
return [obj isEqual:[NSNull null]] ? YES : NO;
}];
Remove the filtered properties from your Mutable leafDict:
[leafDict removeObjectsForKeys:[nullSet allObjects]];
Now when you call fight.winnerID = [dict objectForKey:#"winner"]; winnerID is automatically going to be (null) or nil as opposed to <null> or [NSNull null].
Not relative to this, but I also noticed that it is better to use a NSNumberFormatter when parsing strings to NSNumber, the way I was doing was getting integerValue from a nil string, this gives me an undesired NSNumber of 0, when I actually wanted it to be nil.
Before:
// when [leafDict valueForKey:#"round"] == nil
fight.round = [NSNumber numberWithInteger:[[leafDict valueForKey:#"round"] integerValue]]
// Result: fight.round = 0
After:
__autoreleasing NSNumberFormatter* numberFormatter = [[NSNumberFormatter alloc] init];
fight.round = [numberFormatter numberFromString:[leafDict valueForKey:#"round"]];
// Result: fight.round = nil
I wrote a couple of category methods to strip nulls from a JSON-generated dictionary or array prior to use:
#implementation NSMutableArray (StripNulls)
- (void)stripNullValues
{
for (int i = [self count] - 1; i >= 0; i--)
{
id value = [self objectAtIndex:i];
if (value == [NSNull null])
{
[self removeObjectAtIndex:i];
}
else if ([value isKindOfClass:[NSArray class]] ||
[value isKindOfClass:[NSDictionary class]])
{
if (![value respondsToSelector:#selector(setObject:forKey:)] &&
![value respondsToSelector:#selector(addObject:)])
{
value = [value mutableCopy];
[self replaceObjectAtIndex:i withObject:value];
}
[value stripNullValues];
}
}
}
#end
#implementation NSMutableDictionary (StripNulls)
- (void)stripNullValues
{
for (NSString *key in [self allKeys])
{
id value = [self objectForKey:key];
if (value == [NSNull null])
{
[self removeObjectForKey:key];
}
else if ([value isKindOfClass:[NSArray class]] ||
[value isKindOfClass:[NSDictionary class]])
{
if (![value respondsToSelector:#selector(setObject:forKey:)] &&
![value respondsToSelector:#selector(addObject:)])
{
value = [value mutableCopy];
[self setObject:value forKey:key];
}
[value stripNullValues];
}
}
}
#end
It would be nice if the standard JSON parsing libs had this behaviour by default - it's almost always preferable to omit null objects than to include them as NSNulls.
Another method is
-[NSObject setValuesForKeysWithDictionary:]
In this scenario you could do
[fight setValuesForKeysWithDictionary:dict];
In the header NSKeyValueCoding.h it defines that "Dictionary entries whose values are NSNull result in -setValue:nil forKey:key messages being sent to the receiver.
The only downside is you will have to transform any keys in the dictionary to keys that are in the receiver. i.e.
dict[#"winnerID"] = dict[#"winner"];
[dict removeObjectForKey:#"winner"];
I was stuck with the same problem, found this post, did it in a slightly different way.Using category only though -
Make a new category file for "NSDictionary" and add this one method -
#implementation NSDictionary (SuperExtras)
- (id)objectForKey_NoNSNULL:(id)aKey
{
id result = [self objectForKey:aKey];
if(result==[NSNull null])
{
return nil;
}
return result;
}
#end
Later on to use it in code, for properties that can have NSNULL in them just use it this way -
newUser.email = [loopdict objectForKey_NoNSNULL:#"email"];
Thats it