I have a dictionary, like this:
{"Matt":"Apple", "Calvin":"Nut", "Susie":"Pear"}
I want to check the keys of the dictionary with a string, to see if they contain that string-- and if they do, I want to add their respective value to an array
So, if the input was "a"
the return would be ["Apple", "Nut"] because "Matt" and "Calvin" matched the "a"
Basically looking for some Swift tips,
otherwise I was going to implement it like this:
Grab all keys, put into an array
Filter keys for string value, this is the keyArray
Enumerate over keyArray, and get all their values from the dictionary
Boom have an array of values
You can filter the dictionary, using contains() on each key,
and then extract the corresponding values:
let dict = [ "Matt":"Apple", "Calvin":"Nut", "Susie":"Pear" ]
let input = "a"
let values = Array(dict.filter { $0.key.contains(input) }.values)
print(values) // ["Apple", "Nut"]
Or with flatMap() (renamed to compactMap() in Swift 4.1):
let values = dict.flatMap { $0.key.contains(input) ? $0.value : nil }
print(values) // ["Apple", "Nut"]
Here each dictionary entry is mapped to the value if the key contains
the given string, and to nil otherwise. flatMap() then returns an
array with the non-nil values.
Simply using a filter over the dictionary:
let dict: [String: String] = ["Matt": "Apple", "Calvin": "Nut", "Susie": "Pear"]
func findValuesMatching(search: String, in dict: [String: String]) -> [String] {
return dict
.filter { (key, value) in
return key.range(of: search) != nil
}.map { (key, value) in
return value
}
}
print(findValuesMatching(search: "a", in: dict))
Do it like this:
let dict = ["Matt":"Apple", "Calvin":"Nut", "Susie":"Pear"]
let containsA = dict.filter({ $0.key.lowercased().contains("a") }).map({ $0.value })
Output:
["Apple", "Nut"]
Related
My problem is that this code is case-sensitive. If I have "Sam" and "sam", they will be sorted into different keys. Any way that I can think of doing this is by converting the string into all lowercase, but I want it to stay as normal while being sorted without case-sensitivity:
var dict: [String: [String]] = [:]
for string in array {
if (dict[string] != nil) {
dict[string]?.append(string)
}
else {
dict[string] = [string]
}
}
As it is right now my code would result in:
["Sam": ["Sam"], "sam", ["sam"]]
Instead of what I want:
["Sam": ["Sam", "sam"]]
How can I accomplish this?
You can use reduce(into:) method and assign each element capitalized to the result:
let array = ["Sam", "sam", "SAM"]
let dict: [String: [String]] = array.reduce(into: [:]) {
$0[$1.capitalized, default: []].append($1)
}
print(dict) // ["Sam": ["Sam", "sam", "SAM"]]
If you just want to have case insensitive keys and case sensitive values, from given array, the shortest solution could be something like this:
var dict: [String: [String]] = [:]
array.forEach { dict[$0.lowercased(), default: []] += [$0] }
I am trying to get key and value in a Dictionary while I am able to the key and map it to a dictionary, I am unable to get the value which is an array.
var dict = [String: [String]]
I was able to get the key as an array which is what I want like:
var keyArray = self.dict.map { $0.key }
How can I get the value which is already an array
Use flatMap if you want to flatten the result you get when you use map which is of type [[String]].
let valueArray = dict.flatMap { $0.value } // gives `[String]` mapping all the values
Here is how you get each string count Array
var dict = [String: [String]]()
let countOfEachString = dict.map { $0.value }.map{ $0.count }
Each value is a string array .. so to access each array you need to use map again
I have swift dictionary [String: Any] which I store in UserDefauls as an array [[String: Any]]
what I want to do is replace key: value with another one, e.g. "id": "x:coredataid"with"id": "server id"
I need to loop through array first and then through all key values. Is there any elegant solution for this purposes?
If not how then simple iterate through all key values and all nested levels in dictionary?
I have this code: for (key, value) in params
but it's only for top level keys.
Let me explain more in details. As you see I have phases key which an array. Also each phase contains day key which also an array.
So I don't care actually about key naming, phases it or days whether, what I want is to iterate all of key, values from provided [String: Any] dictionary and check if key contains a value which equal provided string.
As you see currently workoutId equals: <x-coredata://C3C82F5A-8709-4EDC-8AE5-C23C65F220D5/WorkoutEntity/t072831FB-8F5C-4589-85CB-6D084671C097815> I underscore it with red line.
So I want to loop a dictionary to catch this key workoutId and check if this equal <x-coredata://C3C82F5A-8709-4EDC-8AE5-C23C65F220D5/WorkoutEntity/t072831FB-8F5C-4589-85CB-6D084671C097815>
One more time I don't care about workoutId name, key can be actually named as exerciseId or id never mind. I just want to find a value <x-coredata://C3C82F5A-8709-4EDC-8AE5-C23C65F220D5/WorkoutEntity/t072831FB-8F5C-4589-85CB-6D084671C097815> in my entire dictionary and if there are lot of them replace all of them.
The reason why I need it is connected to identifier I store localy which are equals to CoreData identifiers as you my noticed. But when I modified my CoreData records with new identifiers returned from server I want to replace my UserDefaults off-line requests store with new ids.
I've added also modification to this code:
func update(_ dict: [String: Any], set serverId: Any, for localId: String) -> [String: Any] {
var newDict = dict
for (k, v) in newDict {
if let mobileLocalId = v as? String {
if mobileLocalId == localId {
newDict[k] = serverId
} else { newDict[k] = v }
} else if let subDict = v as? [String: Any] {
newDict[k] = update(subDict, set: serverId, for: localId)
} else if let dictionaries = v as? [[String: Any]] {
for dictionary in dictionaries {
newDict[k] = update(dictionary, set: serverId, for: localId)
}
}
}
return newDict
}
but it somehow drop days for me and newDict now looks like this:
(lldb) po newDict
▿ 2 elements
▿ 0 : 2 elements
- key : "position"
- value : 0
▿ 1 : 2 elements
- key : "workoutId"
- value : "5d51723b3faceb53f9d2d5ed"
where actully I susscefully changed identifiers, but now all other key pairs from above example are missed.
Here is a solution with a recursive function that replaces all values for a given key.
func update(_ dict: [String: Any], set value: Any, for key: String) -> [String: Any] {
var newDict = dict
for (k, v) in newDict {
if k == key {
newDict[k] = value
} else if let subDict = v as? [String: Any] {
newDict[k] = update(subDict, set: value, for: key)
} else if let subArray = v as? [[String: Any]] {
var newArray = [[String: Any]]()
for item in subArray {
newArray.append(update(item, set: value, for: key))
}
newDict[k] = newArray
}
}
return newDict
}
Note that it doesn't check what type the existing value is but directly replaces it with the new value. Also the code assumes the only types of nested arrays are arrays of dictionaries.
For the array this function can be used with map
let out = data.map { update($0, set: "newValue", for: "id")}
This recursive function will iterate through all key values:
func iterateThroughAllKeyValues<Key: Hashable, Value>(of dictionary: Dictionary<Key, Value>, execute execution: ((Key, Value))->()) {
for element in dictionary {
if let dictionary = element.value as? [Key: Value] {
iterateThroughAllKeyValues(of: dictionary, execute: execution)
} else {
execution(element)
}
}
}
Also you can achieve calling execution on the main node of any nested dictionary with a little bit of change.
And this is the extension mode:
extension Dictionary {
func iterateThroughAllKeyValues(execute execution: ((Key, Value))->()) {
for element in self {
if let dictionary = element.value as? [Key: Value] {
dictionary.iterateThroughAllKeyValues(execute: execution)
} else {
execution(element)
}
}
}
}
Note: Careful about the order
Usage Example:
let dictionary: [String: Any] = [
"id0": "value0",
"nested": ["id1": "value1"],
"nestedNested": ["id2": "value2",
"nested": ["id3": "value3"]]
]
dictionary.iterateThroughAllKeyValues { (key, value) in
print("key:", key, "Value:", value)
}
Output:
key: id0 Value: value0
key: id1 Value: value1
key: id3 Value: value3
key: id2 Value: value2
I'm trying to figure out the best way in Swift to add values to an Array that is a Value in a Dictionary. I want to build a dictionary of contacts sorted by the first letter of their first name. For example [A : [Aaron, Adam, etc...], B : [Brian, Brittany, ect...], ...]
I found this function:
updateValue(_:forKey:)
And tried using it in a loop:
for contact in self.contacts.sorted() {
self.contactDictionary.updateValue([contact], forKey: String(describing: contact.characters.first))
}
But when I tried to use that it replaced the existing array with a new one. I know I can manually check to see if the key in the dictionary exists, if it does, retrieve the array and then append a new value, otherwise add the new key/value pair but I'm not sure if Swift provides an easier/better way to do this.
Any insight would be much appreciated!
You can use reduce(into:) method (Swift4) and as follow:
let contacts = ["Aaron", "Adam", "Brian", "Brittany", ""]
let dictionary = contacts.reduce(into: [String:[String]]()) { result, element in
// make sure there is at least one letter in your string else return
guard let first = element.first else { return }
// create a string with that initial
let initial = String(first)
// initialize an array with one element or add another element to the existing value
result[initial] = (result[initial] ?? []) + [element]
}
print(dictionary) // ["B": ["Brian", "Brittany"], "A": ["Aaron", "Adam"]]
If you are using Swift3 or earlier you would need to create a mutable result dictionary inside the closure:
let contacts = ["Aaron", "Adam", "Brian", "Brittany", ""]
let dictionary = contacts.reduce([String:[String]]()) { result, element in
var result = result
guard let first = element.first else { return result }
let initial = String(first)
result[initial] = (result[initial] ?? []) + [element]
return result
}
print(dictionary) // ["B": ["Brian", "Brittany"], "A": ["Aaron", "Adam"]]
Note that the result is not sorted. A dictionary is an unordered collection. If you need to sort your dictionary and return an array of (key, Value) tuples you can use sorted by key as follow:
let sorted = dictionary.sorted {$0.key < $1.key}
print(sorted)
"[(key: "A", value: ["Aaron", "Adam"]), (key: "B", value: ["Brian", "Brittany"])]\n"
Swift 4's new dictionary initializers can do it all for you:
let contactInitials = contacts.filter{!$0.isEmpty}.map{ ($0.first!,[$0]) }
let dict = [Character:[String]](contactInitials, uniquingKeysWith:+)
I'm trying to figure out the best way in Swift to add values to an Array that is a Value in a Dictionary. I want to build a dictionary of contacts sorted by the first letter of their first name. For example [A : [Aaron, Adam, etc...], B : [Brian, Brittany, ect...], ...]
I found this function:
updateValue(_:forKey:)
And tried using it in a loop:
for contact in self.contacts.sorted() {
self.contactDictionary.updateValue([contact], forKey: String(describing: contact.characters.first))
}
But when I tried to use that it replaced the existing array with a new one. I know I can manually check to see if the key in the dictionary exists, if it does, retrieve the array and then append a new value, otherwise add the new key/value pair but I'm not sure if Swift provides an easier/better way to do this.
Any insight would be much appreciated!
You can use reduce(into:) method (Swift4) and as follow:
let contacts = ["Aaron", "Adam", "Brian", "Brittany", ""]
let dictionary = contacts.reduce(into: [String:[String]]()) { result, element in
// make sure there is at least one letter in your string else return
guard let first = element.first else { return }
// create a string with that initial
let initial = String(first)
// initialize an array with one element or add another element to the existing value
result[initial] = (result[initial] ?? []) + [element]
}
print(dictionary) // ["B": ["Brian", "Brittany"], "A": ["Aaron", "Adam"]]
If you are using Swift3 or earlier you would need to create a mutable result dictionary inside the closure:
let contacts = ["Aaron", "Adam", "Brian", "Brittany", ""]
let dictionary = contacts.reduce([String:[String]]()) { result, element in
var result = result
guard let first = element.first else { return result }
let initial = String(first)
result[initial] = (result[initial] ?? []) + [element]
return result
}
print(dictionary) // ["B": ["Brian", "Brittany"], "A": ["Aaron", "Adam"]]
Note that the result is not sorted. A dictionary is an unordered collection. If you need to sort your dictionary and return an array of (key, Value) tuples you can use sorted by key as follow:
let sorted = dictionary.sorted {$0.key < $1.key}
print(sorted)
"[(key: "A", value: ["Aaron", "Adam"]), (key: "B", value: ["Brian", "Brittany"])]\n"
Swift 4's new dictionary initializers can do it all for you:
let contactInitials = contacts.filter{!$0.isEmpty}.map{ ($0.first!,[$0]) }
let dict = [Character:[String]](contactInitials, uniquingKeysWith:+)