I got a question regarding filtering an array.
Let's assume I got an array of country names:
let countries = [Albania, Bahrain, Barbados, Denmark, France, Zimbabwe]
now I want to filter this array to check if it contains a certain String let say "ba".
I can do this easily with
countries = countries.filter{ $0.contains("ba")}
which returns
Albania, Bahrain, Barbados, Zimbabwe
But I actually want the order of letters to matter. Therefore, the result "Albania" and "Zimbabwe" should not appear and only "Bahrain" and "Barbados" as their name starts with an Ba.
Is there any way to do this to avoid a huge for loop going through all entites checking individually for each character?
Use .hasPrefix instead of .contains, like this:
print(countries.filter{ $0.hasPrefix("Ba") })
Note that this is case sensitive. BTW, in your example, the problem was not missing order of letters but the fact that .contains respects case as do most methods in swift.
You can take care of the case and the filtering in one step:
let countries = ["Albania", "Bahrain", "Barbados", "Denmark", "France", "Zimbabwe"]
let filtered = countries.filter { $0.lowercased().hasPrefix("ba") } // -> ["Bahrain", "Barbados"]
This lowercases the country names before applying the filter's test, but doesn't change the original array, so the results have the same case.
This is important because you might incorrectly want to do this in two steps for readability:
countries
.map { $0.lowercased()}
.filter { $0.hasPrefix("ba")}
But this returns ["bahrain", "barbados"] because the filter is being applied to the now lowercased array.
Related
I am listing users in a CustomScrollView/SliversList,ListTiles. I have a String field in my firestore and only want to return ListTile of a user, where his String field contains specific words (more than 2). For example, the users fields contain: "Apples, Ice, Bananas, Soup, Peaches, e.g...." and i want to list all users which have apples and bananas inside the field. how can i achieve this?
The only way to do it at the moment (with the way you have it set up) is actually pulling the value and doing a string "contains" or splitting the string into an array and check whether the value is within that array, otherwise I'd advise to refactor that field and make it into an array, that way you can perform a native arrayContainsAny against your field.
For you it will look like this (with your current implementation):
// ... after pulling all users' documents
// let's say your field is called 'foodField':
var criteria = 'Banana';
var fieldContent = doc.data()['foodField'];
// you can either do this:
if (fieldContent.toLowerCase().contains(criteria.toLowerCase())) {
// ...
}
// or you can tokenize it depending on your purposes...
var foodTokens = fieldContent.split(',').map((f) => f.toLowerCase());
if (foodTokens.contains(criteria.toLowerCase()) {
// ...
}
If your Firestore field was an array type, then you could've just done that, while querying:
FirebaseFirestore.instance.collection('users').where('foodField', arrayContainsAny: ['Banana', 'Apples'])
Which then would give you only the users whose foodField contain that value.
As you can see from previous questions on querying where text contains a substring, Firestore does not currently support such text searches. The typical solutions are to either perform part of your filtering in your application code as Roman answered, or to integrate a third-party full-text search solution.
In your specific case though, your string seems to be a list of words, so I'd recommend considering to change your data model to an array of the individual values in there:
"foodFields": ["Apples", "Ice", "Banana", "Soup", "Peaches"]
You can then use array field operators in the query.
While there is no array-contains-all operator, using array-contains you can at least filter on one value in the database, and with array-contains-any you can do on OR like condition.
Another data model would be to store the individual values in a map field with value true for each of them:
"foodFields": {
"Apples": true,
"Ice": true,
"Banana": true,
"Soup": true,
"Peaches": true
}
With such a structure you can perform an AND like query with:
collectionRef
.where('foodFields.Apples', isEqualTo: true)
.where('foodFields.Bananas', isEqualTo: true)
I have in my index a list of object, each of them has an objectID value.
On some search, i want to filter OUT a certain number of them, using there objectID.
For the moment it works with one value as a string, i would like to know how to do for multiple value.
filters = 'NOT objectID:' + objectIDToFilter;
This work for one object, what can i do to apply this for an array of ObjectID. because :
filters = 'NOT objectID:' + arrayObjectID;
does not work.
I was thinking of generating a huge string with an arrayId.map with all my 'NOT objectID:1 AND NOT objectID: 2 ...' but i wanted to know if there is a cleaner way to do it.
I unfortunately misunderstood the line in algolia doc :
Array Attributes: Any attribute set up as an array will match the filter as soon as one of the values in the array match.
This apparently refers to the value itself in Algolia and not the filter
So i did not found a solution on algolia doc, i went for the long string, hope there is no limits on how much filter we can add on a query (found nothing about that).
Here is what i did if someone need it :
let filters = `NOT objectID:${userID}`;
blockedByUsers.map((blockedByUser) => {
filters = filters + ` AND NOT objectID:${blockedByUser}`;
});
If you need to add multiple but don't have a starting point like i do, you can't start the query with an AND , a solution i found to bypass that:
let filters = `NOT objectID:${blockedByUsers[0]}`;
blockedByUsers.map((blockedByUser, i) => {
if (i > 0) filters = filters + ` AND NOT objectID:${blockedByUser}`;
});
There is probably a cleaner solution, but this work. If you have found other solution for that problems i'll be happy to see :)
I have an array of ingredient names that is dynamic and provided per user. I'd like to match it to mongo documents where there is an array of objects called ingredients which has a property name. I've written a query (see below) which will take query parameters from the URL and will return all the documents that have all matching ingredient names, however this search is case sensitive and I'd like it not to be.
I've considered using bson.RegEx with Option: "i", however I'm not sure how to form this query or apply it to an array of strings.
Here is the case sensitive query:
// Check for ingredients, return all recipes that can be made using supplied ingredients
if qryPrms["ingredients"] != nil {
mongodQ["ingredients.name"] = bson.M{"$all": qryPrms["ingredients"]}
}
mongodQ is the bson.M I use to query the collection later in the code. Ideally I could apply RegEx to each element in qryPrms["ingredients"] so it would return closely matching ingredients like cheese would return swiss cheese as well. This is also a more general mongodb question I suppose when it comes to querying with a dynamic array.
I was able to accomplish this using a for loop to build a slice of type bson.RegEx.
if qryPrms["ingredients"] != nil {
var ingRegEx []bson.RegEx
for i := range qryPrms["ingredients"] {
ingRegEx = append(ingRegEx, bson.RegEx{Pattern: qryPrms["ingredients"][i], Options: "i"})
}
mongodQ["ingredients.name"] = bson.M{"$all": ingRegEx}
}
I am trying to store the values of select list in an array variable
a = b.options.each {|option| puts option.attribute_value "value" }
Output :
IN PROGRESS
UPCOMING
FINAL
POSTPONED
CANCELLED
a.to_i
Is it possible to store all values which getting from attribute and store in An array
The element collections in Watir include the Enumerable module, which gives a lot of useful methods for iterating. In particular, it includes a map method that will perform a block on each element and collect the result in an array.
To store the value of all options, you can simply do:
total_list_values = #browser.options.map(&:value)
#=> ["IN PROGRESS", "UPCOMING", "FINAL", "POSTPONED", "CANCELLED"]
I coded it like this and its worked, posted if anyone wanted this
total_list_values = Array.new
body = #browser.options
body.options.each do |option|
total_list_values << option.value
end
I've got an array like that
Word array (
{
translation = (
{
name = Roma;
lang = it;
},
{
name = Rome;
lang = en;
}
);
type = provenance;
value = RMU;
},
{
translation = (
{
name = "Milano";
lang = it;
},
{
name = "Milan";
lang = en;
}
);
type = destination;
value = MIL;
},)
The idea is to filter it using an NSPredicate and receive and an array of dictionaries based on the lang key, I'd like to get something like this made by filtering for lang == it,
Word array (
{
name = Roma;
lang = it;
type = provenance;
value = RMU;
},
{
name = "Milano";
lang = it;
type = destination;
value = MIL;
})
I can't simplify the data because it comes from a "JSON" service.
I've tried different predicates using SUBQUERY but none of them works, documentation about SUBQUERY is pretty poor, I'm missing something, probably the problem is that I'd like to receive an object that is really different from the source.
Of course I'm able to obtain that structure enumerating, I'm wondering if there is a shorter solution
This answer from Dave DeLong link to SUBQUERY explanation gave a me a lot of hints about SUBQUERY, but I'm not able to find a solution to my problem.
Can someone give me a hints about?
You can't do this with a predicate. (Well, you could, but it would be stupidly complex, difficult to understand and maintain, and in the end it would be easier to write the code yourself)
NSPredicate is for extracting a subset of data from an existing set. It only* does filtering, because a predicate is simply a statement that evaluates to true or false. If you have a collection and filter it with a predicate, then what happens is the collection starts iterating over its elements and asks the predicate: "does this pass your test?" "does this pass your test?" "does this pass your test?"... Every time that the predicate answers "yes this passes my test", the collection adds that object to a new collection. It is that new collection that is returned from the filter method.
THUS:
NSPredicate does not (easily) allow for merging two sets of data (which is what you're asking for). It is possible (because you can do pretty much anything with a FUNCTION() expression), but it makes for inherently unreadable predicates.
SO:
Don't use NSPredicate to merge your dataset. Do it yourself.