my questions is about iPhone development.
I'm trying to figure out if there is a way to count ONLY the number of dictionaries within a dictionary.
for example, let's say this is my dictionary
Dictionary contains 5 elements:
string
string
NSDictionary
NSDictionary
NSDictionary
I would like to count only the NSDictionaries... so the return value should be 3.
Is there any way to accomplish this?
Thanks.
NSSet *dictKeys = [myDict keysOfEntriesPassingTest:^(id key, id obj, BOOL *stop) {
return [obj isKindOfClass:[NSDictionary class]];
}];
NSUInteger numberOfDicts = [dictKeys count];
NSDictionary* root = ...;
__block NSUInteger count = 0;
[root enumerateKeysAndObjectsUsingBlock: ^(id key, id obj, BOOL* stop) {
if ( [obj isKindOfClass: NSDictionary.class] ) ++ count;
*stop = NO;
}];
Of course
NSUInteger count = 0;
for (id obj in root) {
if ( [obj isKindOfClass: NSDictionary.class] ) ++ count;
}
will work as well.
__block NSInteger countOfDictionaries = 0;
[dictionary enumerateKeysAndObjectsUsingBlock:(void (^)(id key, id obj, BOOL *stop))block {
if ([obj isKindOfClass:[NSDictionary class]]) {
countOfDictionaries++;
}
}];
As shown above, simply enumerate through every object of your dictionary and keep a count of every object that is an "NSDictionary", by testing the class of the object.
Loop through your NSDictionary by using NSEnumrator and do the following test :
if ([myObject class] == [NSDictionary class]) c++;
Related
I have a NSMutableDictionary and I want to swap values & keys. i.e, after swapping values becomes keys and its corresponding keys with become values All keys and values are unique. Looking for an in place solution because size is very big . Also, the keys and values are NSString objects
NSMutableDictionary *d = [NSMutableDictionary dictionaryWithDictionary:#{
#"key1" : #"value1",
#"key2" : #"value2"}];
for (NSString *key in [d allKeys]) {
d[d[key]] = key;
[d removeObjectForKey:key];
}
NSLog(#"%#", d); // => { value1 : key1,
// value2 : key2 }
Assumptions
unique values (as they will become keys)
values conform to NSCopying (same as above)
no value is equal to any key (otherwise colliding names will be lost in the process)
Here is another way to invert dictionary. The simplest for me.
NSArray *keys = dictionary.allKeys;
NSArray *values = [dictionary objectsForKeys:keys notFoundMarker:[NSNull null]];
[dictionary removeAllObjects]; // In case of huge data sets release the contents.
NSDictionary *invertedDictionary = [NSDictionary dictionaryWithObjects:keys forKeys:values];
[dictionary setDictionary:invertedDictionary]; // In case you want to use the original dictionary.
EDIT: I had written a few lines of codes to get the OP started into the task of creating his own algorithm. The answer was not well received so I have crafted a full implementation of an algorithm that does what he asks, and goes one step further.
Advantages:
Makes no assumptions regarding the contents of the dictionary, for example, the values need not conform to the 'NSCopying' protocol
Transverses the whole hierarchy of a collection, swapping all the keys
It's fast since it uses recursion and fast enumeration
Does not alter the contents of the original dictionary, it creates a brand new one
Code has been implemented through categories to both collections:
#interface NSDictionary (Swapping)
- (NSDictionary *)dictionaryBySwappingKeyWithValue;
#end
#interface NSDictionary (Swapping)
- (NSDictionary *)dictionaryBySwappingKeyWithValue
{
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithCapacity:self.count];
[self enumerateKeysAndObjectsUsingBlock:^(id key, id value, BOOL *stop) {
id newKey = nil;
if ([value isKindOfClass:[NSDictionary class]]) {
newKey = [value dictionaryBySwappingKeyWithValue];
} else if ([value isKindOfClass:[NSArray class]]) {
newKey = [value arrayBySwappingKeyWithValue];
} else {
newKey = value;
}
if (![newKey conformsToProtocol:#protocol(NSCopying)]) {
newKey = [NSValue valueWithNonretainedObject:newKey];
}
mutableDictionary[newKey] = key;
}];
return [NSDictionary dictionaryWithDictionary:mutableDictionary];
}
#end
and...
#interface NSArray (Swapping)
- (NSArray *)arrayBySwappingKeyWithValue;
#end
#implementation NSArray (Swapping)
- (NSArray *)arrayBySwappingKeyWithValue
{
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:self.count];
[self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj isKindOfClass:[NSDictionary class]]) {
NSDictionary *newDict = [obj dictionaryBySwappingKeyWithValue];
mutableArray[idx] = newDict;
} else if ([obj isKindOfClass:[NSArray class]]) {
NSArray *newArray = [obj arrayBySwappingKeyWithValue];
mutableArray[idx] = newArray;
} else {
mutableArray[idx] = obj;
}
}];
return [NSArray arrayWithArray:mutableArray];
}
#end
As an example, assume you have a dictionary with the following structure:
UIView *view = [[UIView alloc] init];
NSDictionary *dict = #{#"1" : #"a",
#"2" : #[ #{ #"5" : #"b" } ],
#"3" : #{#"6" : #"c"},
#"7" : view};
NSDictionary *newDict = [dict dictionaryBySwappingKeyWithValue];
Printing the newDict object in the console will give you this output:
(lldb) po mutableDictionary
{
a = 1;
({b = 5;}) = 2;
{c = 6;} = 3;
"<30b50617>" = 7;
}
As you can see, not only have the keys and values been swapped at the first level of the hierarchy, but deep inside each collection.
"<30b50617>" represents the UIView object wrapped inside a NSValue. Since UIView does not comply to the NSCopying protocol, it needs to be handled this way if you want it to be a key in your collection.
Note: Code was done in a couple of minutes. Let me know if I missed something.
for (NSString *key in [myDictionary allKeys]) {
NSString *value = [responseDataDic objectForKey:key];
[myDictionary removeObjectForKey:key];
[myDictionary addObject:key forKey:value];
}
Assumption:
No key = value;
Complexity:
No extra space required. Will loop through once and replace all key value pairs.
NSArray* allKeys = [theDict allKeys];
NSArray* allValues = [theDict allValues];
NSMutableDictionary* newDict = [NSMutableDictionary dictionaryWithObjects:allKeys forKeys:allValues];
i have an array with dictionaries,
. how to get the index for a specific dictionary... [where I got the data for the dictionary i want to find, but need the index is on]
NSMutableDictionary *dictois = [[NSMutableDictionary alloc]init];
[dictois setObject:#"easySpritedd" forKey:#"Nombre"];
[dictois setObject:#"X" forKey:#"290"];
[dictois setObject:#"Y" forKey:#"300"];
int fooIndex = [self.bloquesArray indexOfObject: dictois];
but as you see i dont know yet how to get the dictionary for comparing in the indexOfObject
thanks!
NSDictionary objects have the following comparison methods:
- (BOOL)isEqualToDictionary:(NSDictionary *)otherDictionary
With the following discussion
Two dictionaries have equal contents if they each hold the same number
of entries and, for a given key, the corresponding value objects in
each dictionary satisfy the isEqual: test.
This should be the case for you. Sadly you cannot change the method which NSArray uses to calculate the indexOfObject: so it can't help you, hence the solution provided by Denis is the best I can think of (unless you fancy subclassing NSArray which I wouldn't recommend).
Just as a complement to Denis' answer you could use the NSArray method
- (NSIndexSet *)indexesOfObjectsPassingTest:(BOOL (^)(id obj, NSUInteger idx, BOOL *stop))predicate
instead of
- (NSUInteger)indexOfObjectPassingTest:(BOOL (^)(id obj, NSUInteger idx, BOOL *stop))predicate
If having several equal objects in the array is a possibility.
Use the following code
NSMutableDictionary *dictois = [[NSMutableDictionary new]autorelease];
[dictois setObject:#"easySpritedd" forKey:#"Nombre"];
[dictois setObject:#"X" forKey:#"290"];
[dictois setObject:#"Y" forKey:#"300"];
int fooIndex = [self.bloquesArray indexOfObjectPassingTest: ^(id obj, NSUInteger idx, BOOL *stop){
if( [[obj class] isKindOfClass: [NSDictionary class]] ) {
BOOL result = [obj isEqualToDictionary: diction];
*stop = result;
return result;
}
*stop = NO;
return NO;
}];
I can use [NSArray indexOfObject: NSString] to get an index of my search for 1 item. But what can I use or do to get an array of returned indices from my search?
thanks
To get multiple indices, you can use indexesOfObjectsPassingTest::
// a single element to search for
id target;
// multiple elements to search for
NSArray *targets;
...
// every index of the repeating element 'target'
NSIndexSet *targetIndices = [array indexesOfObjectsPassingTest:^ BOOL (id obj, NSUInteger idx, BOOL *stop) {
return [obj isEqual:target];
}];
// every index of every element of 'targets'
NSIndexSet *targetsIndices = [array indexesOfObjectsPassingTest:^ BOOL (id obj, NSUInteger idx, BOOL *stop) {
return [targets containsObject:obj];
}];
Support for blocks were added in iOS 4. If you need to support earlier versions of iOS, indexesOfObjectsPassingTest: isn't an option. Instead, you can use indexOfObject:inRange: to roll your own method:
#interface NSArray (indexesOfObject)
-(NSIndexSet *)indexesOfObject:(id)target;
#end
#implementation NSArray (indexesOfObject)
-(NSIndexSet *)indexesOfObject:(id)target {
NSRange range = NSMakeRange(0, [self count]);
NSMutableIndexSet *indexes = [[NSMutableIndexSet alloc] init];
NSUInteger idx;
while (range.length && NSNotFound != (idx = [self indexOfObject:target inRange:range])) {
[indexes addIndex: idx];
range.length -= idx + 1 - range.location;
range.location = idx + 1;
}
return [indexes autorelease];
}
#end
If you don't have access to indexOfObjectsPassingTest, as #outis recommends, you could use indexOfObject:inRange: and loop over the results, updating the range to start after the last result finished, and updating the results into your own NSIndexSet, or NSMutableArray, etc.
Now I'm trying the following and it works.
- (void)findDictionaryWithValueForKey:(NSString *)name {
for (NSDictionary * set in myArray) {
if ([[set objectForKey:#"title"] isEqualToString:name])
\\do something
}
}
EDIT:
I've added one extra argument to the post of bshirley. Now it looks more flexible.
- (NSDictionary *)findDictionaryWithValue:(NSString*)name forKey:(NSString *)key {
__block BOOL found = NO;
__block NSDictionary *dict = nil;
[self.cardSetsArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
dict = (NSDictionary *)obj;
NSString *title = [dict valueForKey:key];
if ([title isEqualToString:name]) {
found = YES;
*stop = YES;
}
}];
if (found) {
return dict;
} else {
return nil;
}
}
Here's one possible implementation using newer API. (I also modified the method to actually return the value). Provided mostly to demonstrate that API. The assumption is that the title is unique to one dictionary within your array.
- (NSDictionary *)findDictionaryWithValueForKey:(NSString *)name {
// ivar: NSArray *myArray;
__block BOOL found = NO;
__block NSDictionary *dict = nil;
[myArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
dict = (NSDictionary *)obj;
NSString *title = [dict valueForKey:#"title"];
if ([title isEqualToString:name]) {
found = YES;
*stop = YES;
}
}];
if (found) {
return dict;
} else {
return nil;
}
}
Use filteredArrayUsingPredicate: method of the array to get all the dictionaries that satisfy your requirement.
NSPredicate * predicate = [NSPredicate predicateWithFormat:#" title MATCHES[cd] %#", name];
NSArray * matches = [myArray filteredArrayUsingPredicate:predicate];
Now matches is the array of dictionaries that have the title key equal to name.
- (void)findDictionaryWithValueForKey:(NSString)name {
for (NSDictionary * set in myArray) {
NSString *s=[NSString stringWithFormat:#"%#",[set objectForKey:#"title"]];
if ([s isEqualToString:name])
\\do something
}
OR
if (s == name])
\\do something
}
}
I will also suggest this way,it would be better if you use a break statement,
- (void)findDictionaryWithValueForKey:(NSString)name {
for (NSDictionary * set in myArray) {
if ([[set objectForKey:#"title"] isEqualToString:name])
\\do something
break;
}
}
As per the NSArray documentation,
valueForKey:
Returns an array containing the results of invoking valueForKey: using key on each of the array's objects.
- (id)valueForKey:(NSString *)key
Parameters
key
The key to retrieve.
Return Value
The value of the retrieved key.
Discussion
The returned array contains NSNull elements for each object that returns nil.
Availability
* Available in Mac OS X v10.3 and later.
EDIT:
try this,
[myArray valueForKey:#"name"];
//this will return array of values, but this actually differ from what to want
I want to take the values from NSMutableArray but want to read from last index to 1st index
thank you
for (id someObject in [someArray reverseObjectEnumerator])
{
//do your thing
}
2 other options:
Simple for-loop (surely not recommended):
for (int i = [array count]-1; i >= 0; ++i)
id value = [array objectAtIndex: i];
Block-based enumeration:
[array enumerateObjectsWithOptions: NSEnumerationReverse
usingBlock: ^(id obj, NSUInteger idx, BOOL *stop){
//do something
}];
Mark's answer is useful, but this form may be useful when you want to mutate the array:
while ([arr count]) {
id obj = [arr lastObject];
// use obj
[arr removeLastObject];
}