I have an NSArray of custom objects that all have a #property name of type NSString. How can I quickly enumerate through the array and create a new array that contains only the objects that have a specific word in their name property?
For instance:
CustomObject *firstObject = [[CustomObject alloc] init];
firstObject.name = #"dog";
CustomObject *secondObject = [[CustomObject alloc] init];
secondObject.name = #"cat";
CustomObject *thirdObject = [[CustomObject alloc] init];
thirdObject.name = #"dogs are fun";
NSMutableArray *testArray = [NSMutableArray arrayWithObjects:firstObject,
secondObject,
thirdObject,
nil];
// I want to create a new array that contains all objects that have the word
// "dog" in their name property.
I know I could use a for loop like so:
NSMutableArray *newArray = [NSMutableArray array];
for (CustomObject *obj in testArray)
{
if ([obj.name rangeOfString:#"dog"].location == NSNotFound) {
//string wasn't found
}
else {
[newArray addObject:obj];
}
}
But is there a more efficient way? Thanks!
NSString *searchString = #"dog";
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"SELF.name contains %#", searchString];
NSArray *filteredArray = [testArray filteredArrayUsingPredicate:predicate];
Please have a look at NSPredicates ! They are highly efficient when you are searching / filtering through array results. This is the documentation!
Related
I have an array of instances of a class called Contact, which has, among others, the following properties:
NSArray *mailAddressList // Array of NSString
NSArray *websiteList // Array of NSString
NSArray *tags // Array of instances of Tag class
The class tag has the following properties:
NSString *name;
UIColor *color;
I want to use NSPredicate to search a string in any property of each Contact. This is the code I have:
if([scope isEqualToString:SCOPE_MAIL] || [scope isEqualToString:SCOPE_WEBSITE])
{
// Search through an array
predicate = [NSPredicate predicateWithFormat:#"ANY SELF.%# contains[c] %#", scope, textSearch];
}
else if([scope isEqualToString:SCOPE_TAG])
{
// Search another object's property
predicate = [NSPredicate predicateWithFormat:#"SELF.%#.name contains[c] %#", scope, textSearch];
}
else
{
// The rest of the properties are instances of NSString
predicate = [NSPredicate predicateWithFormat:#"SELF.%# contains[c] %#", scope, textSearch];
}
Everything works fine except for SCOPE_TAG, it doesn't return any values. I don't think I'm using the predicate correctly.
NOTE: I'm new with NSPredicate so I would like to hear some insights if what I'm doing is not ok
First of all, if you substitute a keypath you should use %K as arg.
Further, I think you are missing the ANY argument in your second query. I think you want a result if any of the tag names contains your textSearch.
To get a better understanding of how predicates work, have a look at the Apple Documentation
I did a quick test and it is still working fine:
NSMutableArray *arrayContacts = [NSMutableArray array];
{
AMContact *contact = [[AMContact alloc] init];
NSMutableArray *arrayTags = [NSMutableArray array];
{
AMTags *tag = [[AMTags alloc] init];
tag.name = #"Test";
[arrayTags addObject:tag];
}
{
AMTags *tag = [[AMTags alloc] init];
tag.name = #"Te2st2";
[arrayTags addObject:tag];
}
{
AMTags *tag = [[AMTags alloc] init];
tag.name = #"No";
[arrayTags addObject:tag];
}
contact.tags = [arrayTags copy];
[arrayContacts addObject:contact];
}
{
AMContact *contact = [[AMContact alloc] init];
NSMutableArray *arrayTags = [NSMutableArray array];
{
AMTags *tag = [[AMTags alloc] init];
tag.name = #"Test";
[arrayTags addObject:tag];
}
contact.tags = [arrayTags copy];
[arrayContacts addObject:contact];
}
NSPredicate *pred = [NSPredicate predicateWithFormat:#"ANY SELF.%K.name contains[c] %#", #"tags", #"Test"];
NSArray *result = [arrayContacts filteredArrayUsingPredicate:pred];
NSLog(#"%#", result);
I have an iPad that reads data from an SQL database. The following code works fine and retrieves 2 fields from each record and reads them into an NSArray.
I now need to read 5 of the fields and I can't help but think that there is a better way of doing it rather than running 5 separate queries through php (the getinfo.php file with the choice parameter set to pick the different fields).
Any pointers to a better method for doing this?
NSString *strURLClass = [NSString stringWithFormat:#"%#%#", #"http://wwwaddress/getinfo.php?choice=1&schoolname=",obsSchoolName];
NSArray *observationsArrayClass = [[NSMutableArray alloc] initWithContentsOfURL:[NSURL URLWithString:strURLClass]];
observationListFromSQL = [[NSMutableArray alloc]init];
NSEnumerator *enumForObsClass = [observationsArrayClass objectEnumerator];
NSString *strURLDate = [NSString stringWithFormat:#"%#%#", #"http://wwwaddress/getinfo.php?choice=5&schoolname=",obsSchoolName];
NSArray *observationsArrayDate = [[NSMutableArray alloc] initWithContentsOfURL:[NSURL URLWithString:strURLDate]];
observationListFromSQL = [[NSMutableArray alloc]init];
NSEnumerator *enumForObsDate = [observationsArrayDate objectEnumerator];
id className, dateOfObs;
while (className = [enumForObsClass nextObject])
{
dateOfObs = [enumForObsDate nextObject];
[observationListFromSQL addObject:[NSDictionary dictionaryWithObjectsAndKeys:className, #"obsClass", dateOfObs, #"obsDate",nil]];
}
Yes, you can do that with less code by "folding" the statements into a loop, and using a mutable dictionary:
// Add other items that you wish to retrieve to the two arrays below:
NSArray *keys = #[#"obsClass", #"obsDate"]; // Key in the dictionary
NSArray *choices = #[#1, #5]; // Choice in the URL string
NSMutableArray *res = [NSMutableArray array];
NSMutableArray *observationListFromSQL = [NSMutableArray array];
for (int i = 0 ; i != keys.count ; i++) {
NSNumber *choice = choices[i];
NSString *strURLClass = [NSString stringWithFormat:#"http://wwwaddress/getinfo.php?choice=%#&schoolname=%#", choice, obsSchoolName];
NSArray *observationsArray = [[NSMutableArray alloc] initWithContentsOfURL:[NSURL URLWithString:strURLClass]];
NSEnumerator *objEnum = [observationsArrayClass objectEnumerator];
NSString *key = keys[i];
NSMutableDictionary *dict;
if (res.count < i) {
dict = res[i];
} else {
dict = [NSMutableDictionary dictionary];
[res addObject:dict];
}
id item;
while (item = [objEnum nextObject]) {
[res setObject:item forKey:key];
}
}
I have one NSArray with names in string objects like this:#[#"john", #"smith", #"alex",
#"louis"], and I have another array that contains lots of names. How can I check that all the objects in the first array are in the second?
NSSet has the functionality that you are looking for.
If we disregard performance issues for a moment, then the following snippet will do what you need in a single line of code:
BOOL isSubset = [[NSSet setWithArray: array1] isSubsetOfSet: [NSSet setWithArray: mainArray]];
Use this code..
NSArray *temp1 = [NSArray arrayWithObjects:#"john",#"smith",#"alex",#"loui,#"Jac", nil];
NSArray *temp2 = [NSArray arrayWithObjects:#"john",#"smith",#"alex",#"loui,#"Rob", nil];
NSMutableSet *telephoneSet = [[NSMutableSet alloc] initWithArray:temp1] ;
NSMutableSet *telephoneSet2 = [[NSMutableSet alloc] initWithArray:temp2];
[telephoneSet intersectSet:telephoneSet2];
NSArray *outPut = [telephoneSet allObjects];
NSLog(#"%#",outPut);
output array contains:
"john","smith","alex","loui
as per your requirement.
Run a loop and use isEqualToStiring to verify whether array1 objects exists in mainArray.
int num_of_matches = 0;
for(NSString *name in mainArray)
{
if(array1 containsObject:name){
num_of_matches++;
}
}
if(num_of_matches == [array1 count]{
// All objects present
}else {
// Matched number is equal of number_of_matches
}
If you just need to check if all objects from array1 are in mainArray, you should just use NSSet
e.g.
BOOL isSubset = [[NSSet setWithArray:array1] isSubsetOfSet:[NSSet setWithArray:mainArray]]
if you need to check which objects are in mainArray, you should take a look at NSMutableSet
NSMutableSet *array1Set = [NSMutableSet setWithArray:array1];
[array1Set intersectSet:[NSSet setWithArray:mainArray]];
//Now array1Set contains only objects which are present in mainArray too
Use NSArray filteredArrayUsingPredicate: method. Its really fast to find out similar types of object in both arrays
NSPredicate *intersectPredicate = [NSPredicate predicateWithFormat:#"SELF IN %#", otherArray];
NSArray *intersectArray = [firstArray filteredArrayUsingPredicate:intersectPredicate];
From above code intersect array gives you same objects which are in other array.
Try this way;
NSArray *mainArray=#[#"A",#"B",#"C",#"D"];
NSArray *myArray=#[#"C",#"x"];
BOOL result=YES;
for(id object in myArray){
if (![mainArray containsObject:object]) {
result=NO;
break;
}
}
NSLog(#"%d",result); //1 means contains, 0 means not contains
You can use the concept of [NSArray containsObject:], where your objects will be from your array1 like you say "john","smith","alex","loui"
NSArray *array1 = [NSArray arrayWithObjects:#"a", #"u", #"b", #"v", #"c", #"f", nil];
NSMutableArray *mainArray = [NSMutableArray arrayWithObjects:#"a", #"u", #"I", #"G", #"O", #"W",#"Z",#"C",#"T", nil];
int j=0;
for(int i=0; i < mainArray.count; i++)
{
if (j < array1.count)
{
for( j=0; j <= i; j++)
{
if([[mainArray objectAtIndex:i] isEqualToString:[array1 objectAtIndex:j]] )
{
NSLog(#"%#",[mainArray objectAtIndex:i]);
}
}
}
}
I have two NSArray objects that I would like to be sorted the same. One contains NSString objects, the other custom Attribute objects. Here is what my "key" NSArray looks like:
// The master order
NSArray *stringOrder = [NSArray arrayWithObjects:#"12", #"10", #"2", nil];
The NSArray with custom objects:
// The array of custom Attribute objects that I want sorted by the stringOrder array
NSMutableArray *items = [[NSMutableArray alloc] init];
Attribute *attribute = nil;
attribute = [[Attribute alloc] init];
attribute.assetID = #"10";
[items addObject:attribute];
attribute = [[Attribute alloc] init];
attribute.assetID = #"12";
[items addObject:attribute];
attribute = [[Attribute alloc] init];
attribute.assetID = #"2";
[items addObject:attribute];
So, what I would like to do is use the stringOrder array to determine the sorting of the items array of custom objects.
How can I do this?
Hereby, I compare directly the index of obj1.assetID in stringOrder with the index of obj2.assetID in stringOrder (using Objective-C literals for #() to transform NSString => NSNumber)
[items sortUsingComparator:^NSComparisonResult(Attribute *obj1, Attribute *obj2) {
return [#([stringOrder indexOfObject:obj1.assetID]) compare:#([stringOrder indexOfObject:obj2.assetID])]
}];
Or without ObjC literals :
[items sortUsingComparator:^NSComparisonResult(Attribute *obj1, Attribute *obj2) {
return [[NSNumber numberWithInt:[stringOrder indexOfObject:obj1.assetID]] compare:[NSNumber numberWithInt:[stringOrder indexOfObject:obj2.assetID]]]
}];
While cwehrungs answer will get the job done, the performance is not great on relatively small arrays.
Here is another method for performing the same kind of sort that is a bit quicker (though still far from perfect):
NSMutableArray *sorted = [NSMutableArray array];
// pre-populate with objects
for (int i = 0; i < stringOrder.count; i++)
{
[sorted addObject:[NSNull null]];
}
// place the items at the correct position
for (Attribute *a in items)
{
NSUInteger idx = [stringOrder indexOfObject:a.assetID];
if (idx != NSNotFound)
{
[sorted setObject:a atIndexedSubscript:idx];
}
}
// finally remove all the unecesarry placeholders if one array was smaller
[sorted removeObject:[NSNull null]];
Comparison
Here are the results form running the two methods on an iPhone 5:
sortUsingComparator:
100 - 0.012 s
1000 - 1.116 s
2000 - 4.405 s
3000 - 9.028 s
prepopulated array
100 - 0.003 s
1000 - 0.236 s
2000 - 0.917 s
3000 - 2.063 s
There are a couple approaches you could take.
You could store your Attribute objects in an NSDictionary, with the keys being the strings in your stringOrder array. Then, you could get a sorted array of the keys and use that to populate whatever view you're using to display them:
NSArray* sortedKeys = [dict keysSortedByValueUsingComparator:^(id obj1, id obj2) {
return [obj1 compareTo:obj2];
}
The other is that you make the sort order an intrinsic property of your Attribute object, so an array of Attributes can be sorted directly. I would only recommend taking this approach if the sort order is actually an intrinsic property of your Attributes object. If it isn't and you do this, you'll wind up storing presentation information where it doesn't belong.
Here's an example:
NSArray* sortedAttrs = [attributes sortedArrayUsingComparator:^(id obj1, id obj2) {
// Perform comparison of Attribute's, ahem, attributes
}
Here is the solution that I came up with that works extremely well. Anyone see performance issues with this?
for (Attribute *a in items) {
int index = [stringOrder indexOfObject:a.assetID];
a.sortOrder = index;
}
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"sortOrder" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSArray *sortedArray = [items sortedArrayUsingDescriptors:sortDescriptors];
Parallel Processing:
Results (quad core):
1. sortme:95 sortby:852345 sorted:95 time:0.052576
2. sortme:54248 sortby:852345 sorted:54243 time:0.264660
-(NSArray *)sortArray:(NSArray *)sortme sortBy:(NSArray *)sortBy{
CFAbsoluteTime time = CFAbsoluteTimeGetCurrent();
NSSet *sortmeSet = [NSSet setWithArray:sortme];
NSMutableDictionary *sortDictionary = [NSMutableDictionary dictionary];
dispatch_queue_t sortDictionaryThread = dispatch_queue_create("my.sortDictionaryThread", DISPATCH_QUEUE_CONCURRENT);
[sortBy enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
if ([sortmeSet containsObject:obj]){
dispatch_barrier_async(sortDictionaryThread, ^{
sortDictionary[obj] = #(idx);
});
}
}];
__block NSArray *sortedArray = nil;
dispatch_barrier_sync(sortDictionaryThread, ^{
sortedArray = [sortDictionary keysSortedByValueUsingSelector:#selector(compare:)];
});
NSLog(#"sortme:%li sortby:%li sorted:%li time:%f",sortme.count,sortBy.count,sortedArray.count, CFAbsoluteTimeGetCurrent() - time);
return sortedArray;
}
I have a custom object called Person that among other things contains an NSString field called descriptor, which stores what sort of person that Person object is (angry, sad, wild, happy, morose, etc). All of my Person objects are in an NSMutableArray, but I would like to store them in an NSMutableDictionary in such a manner:
Key: A, Object: An NSMutableArray where all Person objects have descriptor starting with 'A'
Key: B, Object: An NSMutableArray where all Person objects have descriptor starting with 'B'
Key: C, Object: An NSMutableArray where all Person objects have descriptor starting with 'C'
etc...
I've tried to do this in my code below, and at the comment //POINT 1, the keys and arrays seem to match up, but at //POINT 2, when I print out the complete dictionary, all the keys come up with the same values!
So I wanted to know why the NSMutableArray I seem to have is not being stored as I want it in the NSMutableDictionary?
- (void)buildDictionaryForIndexList {
NSMutableDictionary *tempDict = [[[NSMutableDictionary alloc] init] autorelease];
NSMutableArray *personsStartingWithLetter = [[NSMutableArray alloc] init];
NSMutableArray *indexList = [[[NSMutableArray alloc] init] autorelease];
NSInteger loopCounter = 1;
NSString *firstLetter = [[[NSString alloc] init] autorelease];
for (Person *v in persons) {
firstLetter = [[v descriptor] substringWithRange:NSMakeRange(0, 1)];
if ([indexList containsObject:firstLetter]) {
[personsStartingWithLetter addObject:v];
if (loopCounter == [persons count]) {
[tempDict setObject:personsStartingWithLetter forKey:firstLetter];
}
} else {
if (loopCounter > 1) {
//POINT 1
NSLog(#"%#",[indexList objectAtIndex:[indexList count]-1]);
for (Person *q in personsStartingWithLetter) {
NSLog(#"%#",[q descriptor]);
}
[tempDict setObject:personsStartingWithLetter forKey:[indexList objectAtIndex:([indexList count] - 1)]];
[personsStartingWithLetter removeAllObjects];
}
[indexList addObject:firstLetter];
[personsStartingWithLetter addObject:v];
} // else
loopCounter++;
} // for
//POINT 2
NSEnumerator *enumerator = [tempDict keyEnumerator];
for (NSString *str in enumerator) {
NSLog(#"%#",str);
for (Person *c in [tempDict objectForKey:str]) {
NSLog(#"%#",[c descriptor]);
}
}
self.dictionary = tempDict;
} // buildDictionaryForIndexList
So, for example, at POINT 1 my output is:
A
Angry
Amiable
B
Belligerent
C
Cool
...
W
Wild
but at POINT 2 my output is
T
Wild
J
Wild
A
Wild
...
W
Wild
Change [tempDict setObject:personsStartingWithLetter forKey:[indexList objectAtIndex:([indexList count] - 1)]]; (just after point 1) to [tempDict setObject:[[personsStartingWithLetter copy] autorelease] forKey:[indexList objectAtIndex:([indexList count] - 1)]];. The problem is that NSDictionary copies the key, but retains the value. Therefore, if you add a mutable array to the dictionary and then change it, the array in the dictionary also changes. You need to create a non-mutable copy of the array to put in the dictionary.
The whole method is a bit overcomplicated.
- (void)buildDictionaryForIndexList
{
NSMutableDictionary *tempDict = [[[NSMutableDictionary alloc] init] autorelease];
for (Person *v in persons)
{
NSString* firstLetter = [[v descriptor] substringWithRange:NSMakeRange(0, 1)];
NSMutableArray* personsStartingWithLetter = tempDict [firstLetter];
if (personsStartingWithLetter == nil)
{
personsStartingWithLetter = [NSMutableArray array];
tempDict [firstLetter] = personsStartingWithLetter;
}
[personsStartingWithLetter addObject:v];
} // for
self.dictionary = tempDict;
}
You start with an empty dictionary that will contain arrays. For every person, you check whether there is a suitable array or not, and if there isn't one, you create it. So now there is an array for the person, so you add it to the array. That's all.