Is there any of way (other than looping) of extracting a particular property of all objects in an array. So say there in an array of people. I want to extract all their first names into an array.
Key Value coding will help you with that:
NSArray *result = [people valueForKey:#"firstname"];
I got answer for my question.
This is how we can achieve the same in swift.
let arraytWithProperties = arrayWithObjects.map{ $0.propertyName }
Related
for now i am creating my NSMutableArray using:
#define ARRAY_OF_ORDER_SOURCE [NSArray arrayWithObjects:DICTIONARY_OF_ORDER_SOURCE_ALL,DICTIONARY_OF_ORDER_SOURCE_ECOMMERCE,DICTIONARY_OF_ORDER_SOURCE_PHYSICAL,DICTIONARY_OF_ORDER_SOURCE_INVOICE,DICTIONARY_OF_ORDER_SOURCE_RECURRING,DICTIONARY_OF_ORDER_SOURCE_SALESVU,DICTIONARY_OF_ORDER_SOURCE_RESERVATION,nil]
i want to do some thing like:
if(somethingIstrue)
[ARRAY_OF_ORDER_SOURCE addObject:DICTIONARY_OF_ORDER_SOURCE_ALL]
if(somethingElseIstrue)
[ARRAY_OF_ORDER_SOURCE addObject:DICTIONARY_OF_ORDER_SOURCE_ECOMMERCE]
i am doing this as i need this array in my whole project, i have this in constant.h file.
how can i acheive this using macro??
Thanks.
If you really want to have a macro for this you can have a multiline macro and placed there the logic you want. It is not totally clear to me what you want to achieve but instead of macro I would prefer to have a category on NSMutableArray returning the array or some kind of Util class doing so.
There are numerous things wrong with your question. For starters, you claim you are creating an NSMutableArray, but you are in actuality creating an NSArray. You then try to addObject on the immutable array, which you cannot do.
In your line (note I modified it to add a comment):
if(somethingIstrue) {
// The NSArray isn't assigned to anything and tries to addObject to an NSArray
[ARRAY_OF_ORDER_SOURCE addObject:DICTIONARY_OF_ORDER_SOURCE_ALL]
}
you are not assigning the array to anything (as I already noted it won't work because it is trying to add to an NSArray).
I think you want to do something like:
NSMutableArray *orderedSource = [NSMutableArray array];
if (somethingIsTrue) {
[orderedSource addObject:addObject:DICTIONARY_OF_ORDER_SOURCE_ALL];
}
if (somethingElseIsTrue) {
[orderedSource addObject:addObject:DICTIONARY_OF_ORDER_SOURCE_ECOMMERCE];
}
The question you have to ask yourself is why do you insist on using a macro? You have no real design/approach here, which is why your ideas are coming across as scattered.
If you need to consistently create an array based on a set of constraints, one approach would be to create a class which can vend for you the array you want based on criteria. Or you can just do it where you need to using the approach above.
I want to add an Array which contains a Dictionary to an other Array. So the first Array contains a few items and each item consists of 4 key/value pairs. Now I want to add the first Array to the second on position [i,1] (so the second Array would be a three dimensional array?). How can I achieve this?
here's my code:
NSMutableArray *routenArray = [[NSMutableArray alloc] init];
NSMutableArray *firstArray = [[NSMutableArray alloc] init];
NSDictionary *firstDict = [NSDictionary dictionaryWithObjectsAndKeys:abfahrt,#"Abfahrt", ankunft, #"Ankunft", dauer, #"Dauer", route, #"Route", nil];
[firstArray addObject:firstDict];
for (int i = 0; i < firstArray.count; i++) {
routenArray [i][1] = firstArray [i];
}
You know, you really need to learn the basics of "3D" arrays, and indeed arrays / NSMutableArrays generally.
Fundamentally you use addObject to add an item to an NSMutableArray.
The answer to your question is that you use addObject to add objects to your "outside" array.
The things you add, can themselves me complex data objects like arrays - that's the "3D' part as you're thinking about it.
To access elements of an NSArray (or NSMutableArray), you use firstObject, lastObject, or objectAtIndex.
(You don't use braces[1][17].)
I encourage you to read some basic tutorials on NSArray for Xcode.
Click the "tick" sign to mark my answer as correct, closing this question. Then, forget you ever asked this question :) Read some tutorials, then ask new specific questions about NSArray. Also search here for 1000s of examples and QA.
It's possible you're looking for addObjectsFromArray
Generally to solve problems like this.
Go to the dock for the highest class involved in your problem, in this case NSMutableArray ...
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/Reference/Reference.html
no matter how experienced you are, you can always find amazing stuff in there. Just read through each method available to you; often you find just what you want.
In this case addObjectsFromArray is your gift from above. Next, on this site just search on addObjectsFromArray and you'll find lots of great example code and other incidentalia.
Cheers!
There are no "three dimensional arrays". There is NSArray (and NSMutableArray), and they contain objects. Since NSArray and NSDictionary are themselves objects, an NSArray can contain another NSArray which can contain another NSArray. That doesn't make it three-dimensional. And that's where your problem comes from: "routenArray" (wer mixt hier deutsche und englische Namen? ) doesn't contain any objects. routenArray [0] is nil.
What you are writing:
routenArray [i][1] = firstArray [i];
is just a shortcut for
[[routenArray objectAtIndex:i] replaceObjectAtIndex:1 withObject:[firstArray objectAtIndex:i]];
So this is very much not what you think it is.
I have one NSDictionary and it loads up UITableView. If a user scrolls more and more, I call API and pull new data. This data is again in the form of an NSDictionary. Is it possible to add the new NSDictionary to the existing one?
You looking for this guy:
[NSMutableDictionary addEntriesFromDictionary:]
Make sure your UITableView dictionary is an NSMutableDictionary!
Check it here
Use NSMutableDictionary addEntriesFromDictionary to add the two dictionaries to a new mutable dictionary. You can then create an NSDictionary from the mutable one, but it's not usually necessary to have a dictionary non-mutable.
Is your NSDictionary full of other NSDictionaries? It sounds like you would need an NSMutableArray that you could add NSDictionaries to at the end. Assuming you can control the flow of data coming in and wouldn't run the risk of duplicates in your array, you could certainly append the data.
NSMutableArray *array = [[NSMutableArray alloc] init];
arrayCount = [array count]; // check the item count
[array addObject:dictToAppend];
Without seeing how you are implementing it, I can't provide more detailed code examples. Appending items is easy to do, but know it can only be done with mutable versions of Arrays or Dictionaries. Hope this helps a little.
I have an NSArray of custom objects. Consider that the custom objects have a PageNumber property. I would like to filter my NSArray with a condition like "customObject.PageNumber is distinct".
I know I can loop through the array and eliminate object with duplicate pageNumbers. But is there any easy way to do it? I have tried,
[myarray valueForKeyPath:#"distinctUnionOfObjects.pageNumber"];
It is giving me the unique page numbers (like 7, 8, 9). But I want the custom object itself rather than just page numbers. Can any predicate help me?
I have created a simple library, called Linq to ObjectiveC, which is a collection of methods that makes this kind of problem much easier to solve. In your case you need the Linq-to-ObjectiveC distinct method:
NSArray* itemsWithUniquePageNumbers = [items distinct:^id(id item) {
return [item pageNumber];
}];
This returns an array of objects, each one with a unique page number.
Yes, that is possible with the help of NSPredicate
customObject=[(NSArray*)[myArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"self.PageNumber==%d",pageNumber]] lastObject];
//pageNumber is an integer
The filtered array is an NSArray of your custom objects which is the result of filtering using the predicate. Since your page number is unique, it will return only an array of one object. We get that by passing lastObject message to it.
Refer:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/predicates.html#//apple_ref/doc/uid/TP40001798-SW1
New to Objective-C here...
I have a unique string code as the key that I'd like to use to look up associated values.
It seems an NSDictionary is what I'm looking for but I believe this is only used to lookup one value for a given key.
Can anyone provide the code on how to declare/fill a multidimensional immutable NSDictionary? Also the code to retrieve the values?
Also, please let me know I'm going about this the wrong way
Thanks
EDIT: example of array within a dictionary .... using example data from your comment.
NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];
NSArray *firstSet = [[NSArray alloc] initWithObjects:43, 22];
NSArray *secondSet = [[NSArray alloc] initWithObjects:32, 50];
[myDictionary setValue:firstSet forKey:#"010"];
[myDictionary setValue:secondSet forKey:#"011"];
// Get a value out - should be the 50 that you want
NSInteger *myValue = [[myDictionary objectForKey:#"011"] objectAtIndex:1];
Not tested - but should be 95% right. Does this make sense?
You can make any object you want be the value for a given key in an NSDictionary. This includes NSArray or even another NSDictionary. Using either of these would allow you to associate multiple values with one key.
For nested NSDictionaries or custom KVC-complient classes you can use keyPaths, and for nested NSArrays indexPaths.
Also stackoverflow will give you many examples.