Swift return object of type from an array containing class elements
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Here is a small code I wrote to explain the problem:
class Vehicle{
var name:String = ""
var tyres: Int = 0
}
class Bus:Vehicle{
var make:String = "Leyland"
}
class Car: Vehicle{
var model:String = "Polo"
}
let myVehicles:[Vehicle] = [
Vehicle(),
Car(),
Bus()
]
for aVehicle in myVehicles{
if(aVehicle is Bus){
print("Bus found")
}
}
From the code, I can loop through and get the object of type Bus. However, I need a function to do the same thing and return the element of that type if available. I tried using generics but it does not work. I will need something like this:
func getVehicle(type:T.type)->T?{
// loop through the array, find if the object is of the given type.
// Return that type object.
}
arrays swift object generics subclass
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
add a comment |
Here is a small code I wrote to explain the problem:
class Vehicle{
var name:String = ""
var tyres: Int = 0
}
class Bus:Vehicle{
var make:String = "Leyland"
}
class Car: Vehicle{
var model:String = "Polo"
}
let myVehicles:[Vehicle] = [
Vehicle(),
Car(),
Bus()
]
for aVehicle in myVehicles{
if(aVehicle is Bus){
print("Bus found")
}
}
From the code, I can loop through and get the object of type Bus. However, I need a function to do the same thing and return the element of that type if available. I tried using generics but it does not work. I will need something like this:
func getVehicle(type:T.type)->T?{
// loop through the array, find if the object is of the given type.
// Return that type object.
}
arrays swift object generics subclass
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
add a comment |
Here is a small code I wrote to explain the problem:
class Vehicle{
var name:String = ""
var tyres: Int = 0
}
class Bus:Vehicle{
var make:String = "Leyland"
}
class Car: Vehicle{
var model:String = "Polo"
}
let myVehicles:[Vehicle] = [
Vehicle(),
Car(),
Bus()
]
for aVehicle in myVehicles{
if(aVehicle is Bus){
print("Bus found")
}
}
From the code, I can loop through and get the object of type Bus. However, I need a function to do the same thing and return the element of that type if available. I tried using generics but it does not work. I will need something like this:
func getVehicle(type:T.type)->T?{
// loop through the array, find if the object is of the given type.
// Return that type object.
}
arrays swift object generics subclass
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
Here is a small code I wrote to explain the problem:
class Vehicle{
var name:String = ""
var tyres: Int = 0
}
class Bus:Vehicle{
var make:String = "Leyland"
}
class Car: Vehicle{
var model:String = "Polo"
}
let myVehicles:[Vehicle] = [
Vehicle(),
Car(),
Bus()
]
for aVehicle in myVehicles{
if(aVehicle is Bus){
print("Bus found")
}
}
From the code, I can loop through and get the object of type Bus. However, I need a function to do the same thing and return the element of that type if available. I tried using generics but it does not work. I will need something like this:
func getVehicle(type:T.type)->T?{
// loop through the array, find if the object is of the given type.
// Return that type object.
}
arrays swift object generics subclass
arrays swift object generics subclass
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
asked Mar 17 '17 at 9:50
NareshkumarNareshkumar
1,69821629
1,69821629
add a comment |
add a comment |
4 Answers
4
active
oldest
votes
Use foo as? T to try to cast foo as type T.
for aVehicle in myVehicles{
if let bus = aVehicle as? Bus {
print("Bus found", bus.make)
}
}
Your getVehicle can thus be written as:
func getVehicle<T>() -> T? {
for aVehicle in myVehicles {
if let v = aVehicle as? T {
return v
}
}
return nil
}
let bus: Bus? = getVehicle()
or functionally:
func getVehicle<T>() -> T? {
return myVehicles.lazy.flatMap { $0 as? T }.first
}
let bus: Bus? = getVehicle()
(Note that we need to specify the returned variable as Bus? so getVehicle can infer the T.)
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
2
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writeslet bus: Bus? = getVehicle()not justlet bus = getVehicle(). It's the explicit type ofbusthat pickes the rightT
– JeremyP
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
add a comment |
You can write it like this :
func getVehicle<T>(type:T)-> [T]{
return myVehicles.filter{ $0 is T }.map{$0 as! T }
}
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
add a comment |
You can also use this:
func getVehicle<T>(type: T.Type) -> T? {
return myVehicles.filter { type(of: $0) == type }.first as? T
}
Usage:
getVehicle(type: Bus.self)
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
add a comment |
You can also use this:
let a = array.flatMap({ $0 as? MyTypeClass })
// a == [MyTypeClass] no optional
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
Use foo as? T to try to cast foo as type T.
for aVehicle in myVehicles{
if let bus = aVehicle as? Bus {
print("Bus found", bus.make)
}
}
Your getVehicle can thus be written as:
func getVehicle<T>() -> T? {
for aVehicle in myVehicles {
if let v = aVehicle as? T {
return v
}
}
return nil
}
let bus: Bus? = getVehicle()
or functionally:
func getVehicle<T>() -> T? {
return myVehicles.lazy.flatMap { $0 as? T }.first
}
let bus: Bus? = getVehicle()
(Note that we need to specify the returned variable as Bus? so getVehicle can infer the T.)
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
2
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writeslet bus: Bus? = getVehicle()not justlet bus = getVehicle(). It's the explicit type ofbusthat pickes the rightT
– JeremyP
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
add a comment |
Use foo as? T to try to cast foo as type T.
for aVehicle in myVehicles{
if let bus = aVehicle as? Bus {
print("Bus found", bus.make)
}
}
Your getVehicle can thus be written as:
func getVehicle<T>() -> T? {
for aVehicle in myVehicles {
if let v = aVehicle as? T {
return v
}
}
return nil
}
let bus: Bus? = getVehicle()
or functionally:
func getVehicle<T>() -> T? {
return myVehicles.lazy.flatMap { $0 as? T }.first
}
let bus: Bus? = getVehicle()
(Note that we need to specify the returned variable as Bus? so getVehicle can infer the T.)
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
2
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writeslet bus: Bus? = getVehicle()not justlet bus = getVehicle(). It's the explicit type ofbusthat pickes the rightT
– JeremyP
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
add a comment |
Use foo as? T to try to cast foo as type T.
for aVehicle in myVehicles{
if let bus = aVehicle as? Bus {
print("Bus found", bus.make)
}
}
Your getVehicle can thus be written as:
func getVehicle<T>() -> T? {
for aVehicle in myVehicles {
if let v = aVehicle as? T {
return v
}
}
return nil
}
let bus: Bus? = getVehicle()
or functionally:
func getVehicle<T>() -> T? {
return myVehicles.lazy.flatMap { $0 as? T }.first
}
let bus: Bus? = getVehicle()
(Note that we need to specify the returned variable as Bus? so getVehicle can infer the T.)
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
Use foo as? T to try to cast foo as type T.
for aVehicle in myVehicles{
if let bus = aVehicle as? Bus {
print("Bus found", bus.make)
}
}
Your getVehicle can thus be written as:
func getVehicle<T>() -> T? {
for aVehicle in myVehicles {
if let v = aVehicle as? T {
return v
}
}
return nil
}
let bus: Bus? = getVehicle()
or functionally:
func getVehicle<T>() -> T? {
return myVehicles.lazy.flatMap { $0 as? T }.first
}
let bus: Bus? = getVehicle()
(Note that we need to specify the returned variable as Bus? so getVehicle can infer the T.)
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
edited Mar 17 '17 at 10:10
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
answered Mar 17 '17 at 9:57
kennytmkennytm
410k80920926
410k80920926
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
2
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writeslet bus: Bus? = getVehicle()not justlet bus = getVehicle(). It's the explicit type ofbusthat pickes the rightT
– JeremyP
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
add a comment |
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
2
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writeslet bus: Bus? = getVehicle()not justlet bus = getVehicle(). It's the explicit type ofbusthat pickes the rightT
– JeremyP
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
So, I dont have to specify any class type for this method?
– Nareshkumar
Mar 17 '17 at 10:01
2
2
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writes
let bus: Bus? = getVehicle() not just let bus = getVehicle(). It's the explicit type of bus that pickes the right T– JeremyP
Mar 17 '17 at 10:04
@Nareshkumar. The method is generic. Which type of vehicle is used is inferred from the type of the variable to which it is assigned. See kennytm writes
let bus: Bus? = getVehicle() not just let bus = getVehicle(). It's the explicit type of bus that pickes the right T– JeremyP
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
Functionally solution is quite cool I love it !!
– Oleg Gordiichuk
Mar 17 '17 at 10:04
add a comment |
You can write it like this :
func getVehicle<T>(type:T)-> [T]{
return myVehicles.filter{ $0 is T }.map{$0 as! T }
}
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
add a comment |
You can write it like this :
func getVehicle<T>(type:T)-> [T]{
return myVehicles.filter{ $0 is T }.map{$0 as! T }
}
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
add a comment |
You can write it like this :
func getVehicle<T>(type:T)-> [T]{
return myVehicles.filter{ $0 is T }.map{$0 as! T }
}
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
You can write it like this :
func getVehicle<T>(type:T)-> [T]{
return myVehicles.filter{ $0 is T }.map{$0 as! T }
}
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
answered Mar 17 '17 at 10:00
Oleg GordiichukOleg Gordiichuk
9,98854377
9,98854377
add a comment |
add a comment |
You can also use this:
func getVehicle<T>(type: T.Type) -> T? {
return myVehicles.filter { type(of: $0) == type }.first as? T
}
Usage:
getVehicle(type: Bus.self)
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
add a comment |
You can also use this:
func getVehicle<T>(type: T.Type) -> T? {
return myVehicles.filter { type(of: $0) == type }.first as? T
}
Usage:
getVehicle(type: Bus.self)
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
add a comment |
You can also use this:
func getVehicle<T>(type: T.Type) -> T? {
return myVehicles.filter { type(of: $0) == type }.first as? T
}
Usage:
getVehicle(type: Bus.self)
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
You can also use this:
func getVehicle<T>(type: T.Type) -> T? {
return myVehicles.filter { type(of: $0) == type }.first as? T
}
Usage:
getVehicle(type: Bus.self)
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
answered Mar 17 '17 at 10:23
Kane CheshireKane Cheshire
1,1541117
1,1541117
add a comment |
add a comment |
You can also use this:
let a = array.flatMap({ $0 as? MyTypeClass })
// a == [MyTypeClass] no optional
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
add a comment |
You can also use this:
let a = array.flatMap({ $0 as? MyTypeClass })
// a == [MyTypeClass] no optional
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
add a comment |
You can also use this:
let a = array.flatMap({ $0 as? MyTypeClass })
// a == [MyTypeClass] no optional
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
You can also use this:
let a = array.flatMap({ $0 as? MyTypeClass })
// a == [MyTypeClass] no optional
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
answered Nov 23 '18 at 19:01
YannickStephYannickSteph
7,69123839
7,69123839
add a comment |
add a comment |
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