Refers to data classes feature in Kotlin programming language.
Questions tagged [data-class]
380 questions
19
votes
2 answers
How to let a data class implements Interface / extends Superclass properties in Kotlin?
I have several data classes which include a var id: Int? field. I want to express this in an interface or superclass, and have data classes extending that and setting this id when they are constructed. However, if I try this:
interface B {
var id:…
Edy Bourne
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19
votes
2 answers
Is there a way to identify a Kotlin data class from a regular Kotlin class?
Is there a way to identify a Kotlin data class from a regular Kotlin class? Like using reflection maybe?
Ragunath Jawahar
- 19,513
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18
votes
1 answer
How do I make a python dataclass inherit __hash__?
The following will work, but I'd rather not need to repeat the __hash__ in each subclass. Is there a way to tell the dataclass to inherit the hash function (i.e. not set it to None)?
from dataclasses import dataclass
@dataclass
class Hashable:
…
Brian Bruggeman
- 5,008
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17
votes
1 answer
How to update data classes implementing a common interface
I'm struggling with data classes and polymorphism. I want to benefit from the immutability, but still be able to update my state. For this, I'm hoping to be able to use the copy function.
Let's give an example. I have this class hierarchy:
interface…
Stim
- 1,455
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15
votes
2 answers
How should I add a field containing a list of dictionaries in Marshmallow Python?
In Marshmallow in order to have a list field you can use:
include_in = fields.List(cls_or_instance=fields.Str(),
default=['sample1', 'sample2'])
This is OK, but I have a new requirement to have a list of dictionaries in a…
Alireza
- 6,497
- 13
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15
votes
2 answers
Access function before calling superclass constructor in Kotlin data class
I'm using data classes in Kotlin to significantly reduce the amount of Java code I would otherwise have to write.
However, in one of my Java classes, I'm not sure what to do to achieve the same result in Kotlin.
My Java class looks a bit like…
Farbod Salamat-Zadeh
- 19,687
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14
votes
2 answers
Is there any way to transform the value of a property at data class construction time?
When creating a data class I frequently find that I want to transform one of the properties, usually to normalize it or to make a defensive copy. For example, here I want productCode to always be lowercase:
data class Product(val productCode:…
Laurence Gonsalves
- 137,896
- 35
- 246
- 299
14
votes
2 answers
The form's view data is expected to be an instance of class ... but is a(n) string
I am currently receiving the following error:
"The form's view data is expected to be an instance of class Symfony\Component\HttpFoundation\File\File, but is a(n) string. You can avoid this error by setting the "data_class" option to null or by…
P.Belberov
- 503
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13
votes
1 answer
Kotlin: sealed class cannot "contain" data classes? Why?
OK, now that Kotlin is officially out and I am starting to play with it again, I am quite confused that I need to choose between the advantages of sealed and data but somehow can't have both.
This, for example, seems to make sense to me, but does…
david.mihola
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12
votes
1 answer
Is it possible to nest dataclass in kotlin?
I'm trying to achieve similar data class definition like the following C one:
struct A {
int b;
struct {
int d;
} c;
};
According to Dmitry Jemerov it is possible, but he didn't provide any code…
majkrzak
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12
votes
3 answers
Deserialize a Firebase Data-Snapshot to a Kotlin data class
Hi I have a Kotlin data class as follows
data class User (
@get:Exclude val gUser: Boolean,
@get:Exclude val uid: String,
@get:PropertyName("display_name") val displayName: String,
@get:PropertyName("email") val…
aidan8181
- 175
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- 7
11
votes
1 answer
How to test data class on Kotlin?
I have data class'es in my Kotlin project, what I use for JSON Rest responses..
Example:
data class WeatherResponse(val city: String, val temperature: Double, val humidity: Double)
To fullfill code coverage constraints, I would like to write some…
Noam Silverstein
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- 2
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- 18
11
votes
3 answers
How to ignore a filed of Entity with Room
I have a data class that I created an Entity from that for my database.
this is my data class:
@Entity
@Parcelize
data class Tapligh(
@PrimaryKey(autoGenerate = true)
var id: Long,
@SerializedName("title") var title: String?,
…
Ehsan
- 2,676
- 6
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- 56
11
votes
3 answers
How to deserialize inherited Kotlin data classes with Gson
In an Android App I need to deserialize Json data for Kotlin data classes, with a single abstraction level. But I don't have any idea, to place correct properties in constructors.
As a simple version, let's say I have a Shape:
abstract class…
elcolto
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- 11
11
votes
2 answers
Kotlin data classes and nullable types
I'm new to Kotlin and I don't know why compiler complains about this code:
data class Test(var data : String = "data")
fun test(){
var test: Test? = Test("")
var size = test?.data.length
}
Compiler complains with test?.data.length, it says…
Victor Manuel Pineda Murcia
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