I'm struggeling with an error occurring when trying to populate an array with the filtered results of another array.
I've defined a global array named allArray in the .h-file, this array is containing about 100 objects. Then, I want the user to be able to search for a specific object, and I've tried to develop it using predicates:
-(IBAction)searchChanged:(id)sender {
//The searchfield's value has been changed.
NSString *searchString = searchField.text;
NSPredicate *searchPredicate = [NSPredicate predicateWithFormat:#"self CONTAINS[c] %#", searchString];
NSMutableArray *tempSearchArray = [allArray filterUsingPredicate:searchPredicate];
[filteredArray removeAllObjects];
[filteredArray addObjectsFromArray:tempSearchArray];
}
I end up getting an error when I create tempSearchArray.
Initializing 'NSMutableArray *__strong' with an expression of
incompatible type 'void'
filterUsingPredicate doesn't return an array, it returns nothing(void).
From the description:
"Evaluates a given predicate against the array’s content and leaves only objects that match"
You should instead use:
filteredArrayUsingPredicate
As the Docs will tell you, filterUsingPredicate has a void return value.
See here:
NSMutableArray Class reference
That means that you cannot assign that return value to another array.
You need to use this method on the original array, along the lines of
[allArray filterUsingPredicate:somePredicate];
arrArray will be stripped of any elements that dont match the predicate.
Now proceed with these results as you wish.
Have Fun
filterUsingPredicate returns a void and not an array. You might want to consider using a filteredArrayUsingPredicate instead
Related
As part of an autocomplete box, I am searching names within an array of contacts. However, after the user picks a name from the suggested List, I need to grab the id of the contact which is in the array of contact objects but not the array of names that appear in the suggest box. I've been working with just the names as that's what I want to display in the suggestion box but have an array of contacts as well.
How would I convert code below (probably using key values) to search the name dimensions of an array of objects instead of an array of names so as to keep track of the ids of the objects. I am kind of fuzzy on arrays and key values.
//the array being searched looks something like #[#"John", #"Dave", #"Sam", #"Xian", #"Ahmed", #"Johann"];
//I want to search the names in an array that looks something like:
(
{
first = "John";cid = 2;},
{
first = "Dave";cid = 44;},
{
first = "Xian";cid=99})
//this code works great to search names but I lose track ids. Thank you for any suggestions.
-(void)searchArray: (NSMutableArray*) array forString: (NSString *) term {
[_contactsSuggested removeAllObjects];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"SELF contains[c] %#",term];
NSArray *tempArray = [array filteredArrayUsingPredicate:predicate];
_contactsSuggested = [NSMutableArray arrayWithArray:tempArray];
[_autocompleteTableView reloadData];
}
Create a Contact object. Give it a name property, an id property, and any other properties you need. Then write code that searches an array of Contact objects rather than just an array of names. You could then create a predicate using predicateWithBlock to filter the items that match your name property.
I'm trying to do a simple predicate filter on an array of objects.
The objects in the array have 2 properties, displayValue and value. I am trying to filter based on a search string and I get a crash.
NSPredicate *pred = [NSPredicate predicateWithFormat:#"displayValue CONTAINS[cd] %#", searchString];
NSArray *results = [_data filteredArrayUsingPredicate:pred];
what exactly is incorrect about this format that it causes a Can't use in/contains operator with collection 100 (not a collection) crash?
I was able to reproduce your problem. This happens if the displayValue of one of the objects
is not a NSString, but some different type.
From your error message, I assume that you assigned an NSNumber, for example
obj.displayValue = #100;
somewhere in your code. The "CONTAINS" predicate works only with strings, so you must assign
only string values to the property.
Therefore, you should define the type of the property as
NSString * instead of id, and check the assignments to that property.
If you really need to keep the id type and store different kinds of objects in that property,
then you cannot use the "CONTAINS" operator in the predicate. A direct comparison
with #"displayValue == %#" would work, however.
UPDATE: As a workaround, you could use the description method, which converts any object
to a string, in particular it converts a NSNumber to its string representation. So the following could work:
[NSPredicate predicateWithFormat:#"displayValue.description CONTAINS[cd] %#", searchString];
The drawback is that the exact description format is not documented.
Another solution could be to use a block-based predicate, where you can check the type
of each object and perform the appropriate comparison.
I have a bit of a hard time writing a predicate for my search functionality and thought you'd be bale to help. So basically I have two arrays of NSNumbers. I want my predicate to satisfy the following:
If a number's integerValue in array A matches any integerValue in array B.
I don't want to use any sort of loop for this solution. Here's what I have so far
ANY integerValue == ANY //how do I pass the entire array here and ask for the integerValue of each member?
The ANY operator will handle that.
Since it is a bit difficult to say from your question which of the arrays is "self" in normal predicate parlance, I'll write it without a self:
NSArray *arrayA = #[#2, #3, #7];
NSArray *arrayB = #[#2, #4, #9];
NSPredicate *pred = [NSPredicate predicateWithFormat: #"ANY %# IN %#", arrayA, arrayB];
Due to the lack of a "self", it will have to be evaluated with nil as the object, but that works fine:
BOOL matched = [pred evaluateWithObject: nil];
If you prefer to have a "self" in the predicate, you can just enter it:
NSPredicate *pred = [NSPredicate predicateWithFormat: #"ANY self IN %#", arrayB];
BOOL matched = [pred evaluateWithObject: arrayA];
The result is the same.
A small conceptual comment
The predicate above evaluates to true if any integer is included in both arrays, which is how I read your question.
This means that, conceptually speaking, you seem to be testing whether two sets of numbers intersect each other. NSSet's method intersectsSet: checks that, so another way to do the test would be to keep your numbers as sets and test for intersection:
matched = [setA intersectsSet: setB];
I know it's not precisely what you asked for (predicates and all) but another way is to use NSArray's - (id) firstObjectCommonWithArray:(NSArray *)otherArray, which would return nil if no common object can be found.
BOOL arraysIntersect = [array1 firstObjectCommonWithArray:array2] != nil;
One caveat though is that it would use its own object equality rules when comparing two objects, meaning if two objects are NSNumber instances, it will compare them using NSNumber's compare: method. But the same goes for the predicate-based solution proposed so far.
I'm sure this question has been asked but I don't know what to search on.
I have array of Message objects with the following fields {selected[BOOL], messageText[STR]}. I want to filter this array to get only the objects with selected=TRUE. So far so good.
NSArray *messagesFiltered = [self.fetchedResultsController.fetchedObjects filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"selected == TRUE"]];
However, I don't need the objects themselves in the returned array, I need an array of the messageText strings. How to modify predicate to return only the messageText strings and not the whole object?
That's not really the job of a predicate. Predicates are only for filtering, not modifying, the array you apply them to.
However, there's a fun little trick: the method -valueForKey: will apply the kind of transform you want to your array. Just call it with the messageText key that you want:
NSArray *messagesFiltered = [self.fetchedResultsController.fetchedObjects filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"selected == TRUE"]];
NSArray *realMessages = [messagesFiltered valueForKey:#"messageText"];
On an array, -valueForKey: asks each element for a value for the given key, then returns an array of everything the elements returned. (Any element that returns nil for the key you pass shows up as [NSNull null] in the resulting array.)
I have an NSArray that I want to filter out certain objects using an NSPredicate, I was hoping I could use NOT IN since I saw that I can easily do an IN.
So I have my array:
self.categoriesList
Then I get the values I want to remove:
NSArray *parentIDs = [self.cateoriesList valueForKeyPath:#"#distinctUnionOfObjects.ParentCategoryID"];
This gives me a list of ParentCategoryID's for categories I DO NOT want to display, so I figure I can use an NSPredicate to remove them:
self.cateoriesList = [self.cateoriesList filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"CategoryID NOT IN %#",parentIDs]];
This fails:
reason: 'Unable to parse the format string "CategoryID NOT IN %#"'
If I wanted to use just IN that works perfectly of course.
What about NOT (CategoryID IN %#)?
How about using NONE?
[NSPredicate predicateWithFormat:#"NONE CategoryID IN %#", parentIDs];