Dictionary does not have a member named filter - but it should, shouldn't it? - xcode

Question

I'm trying to get code from github for auto-completion to work, but am stuck with an error on line 6 (data.filter) that Dictionary does not have a member named filter. But everything I read in the documentation suggests dictionaries should have a filter method. I've tried every possible combination of unwrapping, self, etc, but the compiler then registers these changes as the error.
Obviously something is going on that I do not understand - any guidance is appreciated.
var data = Dictionary<String, AnyObject>()
func applyFilterWithSearchQuery(filter : String) -> Dictionary<String, AnyObject>
{
var lower = (filter as NSString).lowercaseString
if (data.count > 0) {
var filteredData = data.filter ({
if let match : AnyObject = $0["DisplayText"]{
return (match as NSString).lowercaseString.hasPrefix((filter as NSString).lowercaseString)
}
else{
return false
}
})
}
return filteredData
}

Answer 1

Never heard of dictionary filters - where have you read about that? Arrays do have a filter method, but not dictionaries. What you can do is filter keys or values (accessible via the respective dictionary properties).
You can implement a custom filter on a dictionary with the following code:
var filtered = dict.keys.filter { $0.hasPrefix("t") }.map { (key: $0, value: dict[$0]) }
var newDict = [String : AnyObject]()
for element in filtered {
newDict[element.key] = element.value
}
which filter keys, then maps each key to a (key, value) tuple, then add each tuple to a new dictionary.
Note that to filter keys I used hasPrefix("t") - replace that with something more appropriate to your case

Answer 2

var data = Dictionary<String, AnyObject>()
func applyFilterWithSearchQuery(filter: String) -> [String : AnyObject] {
var lower = filter.lowercaseString
var filteredData = [String : AnyObject]()
if (!data.isEmpty) {
Swift.filter(data) {
(key, value) -> Bool in
if key == "DisplayText" {
filteredData[key] = (value as? String)?.lowercaseString.hasPrefix(lower)
}
return false
}
/* use map function works too
map(data) {
(key, value) -> Void in
if key == "DisplayText" {
filteredData[key] = (value as? String)?.lowercaseString.hasPrefix(lower)
}
}
*/
}
return filteredData
}