Can each index of array hold the NSDictionary?
Thank You.
Yes, the value of an NSArray can resolve to an object identifier for an NSDictionary. However, the array doesn't "hold" the NSDictionary, nor can the index of an NSArray be an NSDictionary. An index from an Array is always an integer value.
An NSArray can hold any type of object, so yes, putting an NSDictionary in an NSArray works just fine.
You sure can, here is an example:
NSDictionary *dict1 = [[NSDictionary alloc] initWithObjectsAndKeys:
#"value1", #"key1", #"value2", #"key2", nil];
NSDictionary *dict2 = [[NSDictionary alloc] initWithObjectsAndKeys:
#"Billy", #"Goat", #"Rover", #"Dog", nil];
NSArray *arrayWithDictionaries = [[NSArray alloc] initWithObjects:
dict1, dict2, nil];
[dict1 release];
[dict2 release];
Related
I have one NSDictionary and one NSMutableArray And I want store many object from NSDictionary into NSMutableArray from one key but I dont know about it.
this is my code :
//NSArray * a = [[NSArray alloc]initWithObjects:#"1",#"2",#"3",#"4",#"7",#"9", nil];
//NSArray *b = [[NSArray alloc]initWithObjects:#"1",#"2",#"3",#"4",#"5",#"0", nil];
NSDictionary * dic = [NSDictionary dictionaryWithObjectsAndKeys:a,#"number1",b,#"number2", nil];
NSMutableArray *array = [NSMutableArray alloc].... ?
I want store object in number1 key from NSDictionary in NSMutableArray
Since it appears that you store arrays as NSDictionary elements, you can do this:
NSMutableArray *array = [[NSMutableArray alloc] initiWithArray:dic[#"number1"]];
or
NSMutableArray *array = [NSMutableArray arrayWithArray:dic[#"number1"]];
To add object into NsDictionary Array do:
NSMutableDictionary * datos = [array objectAtIndex:i];
[datos setObject:#"hola" objectForKey#"newKey"];
I have a small doubt that is I have an NSArray which contains the following 4 objects:
Genesis, 1 Kings, leviticus, 2 Kings
I want to sort this array in dictionary order like i want an expected output like this
1 Kings, 2 Kings, Genesis, leviticus
How can this be achieved?
Go to this link:
https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Collections/Articles/Arrays.html#//apple_ref/doc/uid/20000132-SW5
This is Apple documentation and your problem is solved over there.
Check out the example.
//First create the array of dictionaries
NSString *last = #"lastName";
NSString *first = #"firstName";
NSMutableArray *array = [NSMutableArray array];
NSArray *sortedArray;
NSDictionary *dict;
dict = [NSDictionary dictionaryWithObjectsAndKeys:
#"Jo", first, #"Smith", last, nil];
[array addObject:dict];
dict = [NSDictionary dictionaryWithObjectsAndKeys:
#"Joe", first, #"Smith", last, nil];
[array addObject:dict];
dict = [NSDictionary dictionaryWithObjectsAndKeys:
#"Joe", first, #"Smythe", last, nil];
[array addObject:dict];
dict = [NSDictionary dictionaryWithObjectsAndKeys:
#"Joanne", first, #"Smith", last, nil];
[array addObject:dict];
dict = [NSDictionary dictionaryWithObjectsAndKeys:
#"Robert", first, #"Jones", last, nil];
[array addObject:dict];
//Next we sort the contents of the array by last name then first name
// The results are likely to be shown to a user
// Note the use of the localizedCaseInsensitiveCompare: selector
NSSortDescriptor *lastDescriptor =[[NSSortDescriptor alloc] initWithKey:last
ascending:YES
selector:#selector(localizedCaseInsensitiveCompare:)];
NSSortDescriptor *firstDescriptor =
[[NSSortDescriptor alloc] initWithKey:first
ascending:YES
selector:#selector(localizedCaseInsensitiveCompare:)];
NSArray *descriptors = [NSArray arrayWithObjects:lastDescriptor, firstDescriptor, nil];
sortedArray = [array sortedArrayUsingDescriptors:descriptors];
This code is an example from Apple documentation.
You can sort an array of NSString alphabetically like this:
NSArray *sortedArray = [myArray sortedArrayUsingSelector:#selector(caseInsensitiveCompare:)];
Aim: To obtain an NSArray containing unique keys for given NSDictionary(s) using elegant code
Example Code with Current Working Solution:
NSArray *data = [[NSArray alloc] initWithObjects:
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:1], #"a", [NSNumber numberWithInt:2], #"b", nil],
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:3], #"b", [NSNumber numberWithInt:4], #"c", nil],
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:5], #"a", [NSNumber numberWithInt:6], #"c", nil],
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:7], #"b", [NSNumber numberWithInt:8], #"a", nil],
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:8], #"c", [NSNumber numberWithInt:9], #"b", nil],
nil];
// create an NSArray of all the dictionary keys within the NSArray *data
NSMutableSet *setKeys = [[NSMutableSet alloc] init];
for (int i=0; i<[data count]; i++) {
[setKeys addObjectsFromArray:[[data objectAtIndex:i] allKeys]];
}
NSArray *arrayKeys = [setKeys allObjects];
NSLog(#"arrayKeys: %#", arrayKeys);
Which returns the desired array of keys:
2012-06-11 16:52:57.351 test.kvc[6497:403] arrayKeys: (
a,
b,
c
)
Question: Is there a more elegant way of approaching this? Surely there must be some KVC approach that can get all the keys without having to iterate through the array? I've been looking at Apple Developer Documentation and can't see a solution. Any ideas? (looking at purely elegance of code rather than performance).
Normally you could use KVC by doing something like this:
NSArray *uniqueKeys = [data valueForKeyPath:#"#distinctUnionOfArrays.allKeys";
However NSDictionary overrides the valueForKey: selector which is used by the KVC internals, so this will not work correctly.
The documentation for NSDictionary's valueForKey: method tells us that:
If key does not start with “#”, invokes objectForKey:. If key does start with “#”, strips the “#” and invokes [super valueForKey:] with the rest of the key.
So we just insert an # before allKeys:
NSArray *uniqueKeys = [data valueForKeyPath:#"#distinctUnionOfArrays.#allKeys"];
And we get what we want:
(lldb) po [data valueForKeyPath:#"#distinctUnionOfArrays.#allKeys"]
(id) $14 = 0x07bb2fc0 <__NSArrayI 0x7bb2fc0>(
c,
a,
b
)
This is less ugly, and possibly marginally faster, I suppose:
NSMutableSet *setKeys = [[NSMutableSet alloc] init];
for (NSDictionary* dict in data) {
for (id key in [dict keyEnumerator]) {
[setKeys addObject:key];
}
}
But you're not doing a particularly common operation, so I wouldn't expect to find some incredibly elegant method. If that's what you want, go learn Haskell.
You could try this:
NSMutableSet *setKeys = [[NSMutableSet alloc] init];
for(NSDictionary *dict in data) {
[setKeys addObjectsFromArray:[dict allKeys]];
}
NSArray *arrayKeys = [setKeys allObjects];
If you prefer blocks you could use this:
[data enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
[setKeys addObjectsFromArray:[obj allKeys]];
}];
Not sure why I get "Missing sentinel in function call?"
NSMutableArray *kkk = [NSMutableArray arrayWithObjects: #"a", #"b", #"cat", #"dog", nil];
ppp = [NSMutableArray arrayWithCapacity:3];
[ppp addObject:[[NSMutableArray alloc] initWithObjects: kkk]]; // <<--- Missing sentinel in function call
[ppp addObject:[[NSMutableArray alloc] initWithObjects: kkk, nil]]; //<<--- change, but it falls out
NSLog(#"Working: %# %#", [[ppp objectAtIndex:0] objectAtIndex:3], [[ppp objectAtIndex:0] objectAtIndex:2] );
initWithObjects: must be terminated with a trailing nil. Since it is a single object, you should be a able to use initWithObject:. That said, you will be leaking the array like this. Do
[ppp addObject:[NSMutableArray arrayWithObject:kkk]];
There is one more problem with the piece of code here,
NSMutableArray *kkk = [NSMutableArray arrayWithObjects: #"a", #"b", #"cat", #"dog", nil];
ppp = [NSMutableArray arrayWithCapacity:3];
[ppp addObject:[[NSMutableArray alloc] initWithObjects: kkk, nil]];
You are creating a three dimensional array. So
NSLog(#"Working: %# %#", [[ppp objectAtIndex:0] objectAtIndex:3], [[ppp objectAtIndex:0] objectAtIndex:2] );
is wrong.
NSLog(#"Working: %# %#", [[[ppp objectAtIndex:0] objectAtIndex:0] objectAtIndex:3], [[[ppp objectAtIndex:0] objectAtIndex:0] objectAtIndex:2] );
should log proper values.
However if you need a two dimensional array based on your log statement, I would say you need to do this instead,
[ppp addObject:kkk];
You need to add nil as the last object in the list.
[ppp addObject:[[NSMutableArray alloc] initWithObjects: kkk, nil]];
Basically it tells the method to stop looking for more objects. Without that, it can look at a bad pointer and crash.
I tried to insert NSDictionary's in a NSMutableDictionary. There is no error but it won't work, it remains empty.
Here's my code:
NSMutableDictionary *einnahmen = [[NSMutableDictionary alloc] initWithCapacity:20];
NSArray *objects = [NSArray arrayWithObjects:
name,
[NSNumber numberWithInt: x],
[NSNumber numberWithInt: y],
[NSNumber numberWithInt: z],
nil];
NSArray *keys = [NSArray arrayWithObjects:
#"name",
#"startJahr",
#"zins",
#"entnahmefaehig",
nil];
NSDictionary *entry = [NSDictionary dictionaryWithObjects:objects forKeys:keys];
[einnahmen setObject:entry forKey:#"name"]; //seems not to work
After [einnahmen setObject:entry the Debugger shows this:
I have solved this problem. The following code was in the wrong init-method:
NSMutableDictionary *einnahmen =
[[NSMutableDictionary alloc] initWithCapacity:20];
The compiler should show a error.