How to make a setter private in Kotlin for non-final variables?

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I need to create a data class like so

data class Cat(var toys:Int=3, val type:String):Animal(){

    ...

}

Animal is an abstract class with fields for eyes and legs,etc.

I don't want callers to be able to set toys directly. But I want to be able to do some work with toys such as

fun addQuota(){toys+=4}

how do I complish this cleanly? I still want a public getter, a private settter, but I don't want the variable to be final. And also, this data class is an Entity for Room.

asked Nov 26 '18 at 21:14

salyela

698

add a comment |

I need to create a data class like so

data class Cat(var toys:Int=3, val type:String):Animal(){

    ...

}

Animal is an abstract class with fields for eyes and legs,etc.

I don't want callers to be able to set toys directly. But I want to be able to do some work with toys such as

fun addQuota(){toys+=4}

how do I complish this cleanly? I still want a public getter, a private settter, but I don't want the variable to be final. And also, this data class is an Entity for Room.

asked Nov 26 '18 at 21:14

salyela

698

add a comment |

I need to create a data class like so

data class Cat(var toys:Int=3, val type:String):Animal(){

    ...

}

Animal is an abstract class with fields for eyes and legs,etc.

I don't want callers to be able to set toys directly. But I want to be able to do some work with toys such as

fun addQuota(){toys+=4}

how do I complish this cleanly? I still want a public getter, a private settter, but I don't want the variable to be final. And also, this data class is an Entity for Room.

asked Nov 26 '18 at 21:14

salyela

698

I need to create a data class like so

data class Cat(var toys:Int=3, val type:String):Animal(){

    ...

}

Animal is an abstract class with fields for eyes and legs,etc.

I don't want callers to be able to set toys directly. But I want to be able to do some work with toys such as

fun addQuota(){toys+=4}

how do I complish this cleanly? I still want a public getter, a private settter, but I don't want the variable to be final. And also, this data class is an Entity for Room.

android kotlin android-room android-architecture-components

asked Nov 26 '18 at 21:14

salyela

698

asked Nov 26 '18 at 21:14

salyela

698

asked Nov 26 '18 at 21:14

salyela

698

asked Nov 26 '18 at 21:14

salyela

698

asked Nov 26 '18 at 21:14

salyela

698

add a comment |

3 Answers
3

active

oldest

votes

You can do this by using the property of the constructor as backing field for the toys property:

data class Cat(val type: String, private var toysField: Int = 3 ):Animal(){



    var toys = toysField

    private set(value){

        toysField = value

    }



    fun addQuota(){toys += 4}



}



abstract class Animal

I hope this works with room.

Source https://discuss.kotlinlang.org/t/private-setter-for-var-in-primary-constructor/3640/10

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

thanks for replying. Your answer should definitely work, but I found a simpler solution, which I am providing as an answer as well. Thanks! +1

– salyela
Nov 26 '18 at 23:48

I finally got a chance to test this code and it actually doesn't work. Here is the version that works: var toys = toysField *n*/ private set(value){ *n*/ toysField = value *n*/ } *n*/ get()=toysField

– salyela
Nov 30 '18 at 20:50

What part does not work and how does adding the getter change that?

– leonardkraemer
Nov 30 '18 at 21:03

add a comment |

It turns out the following works:

data class Cat(private var toys:Int=3, val type:String):Animal(){

    ...

    fun getToys()=toys

}

answered Nov 26 '18 at 23:19

salyela

698

it works, but it's not really idiomatic. the solution with private set is preferred

– Lovis
Nov 27 '18 at 12:59

Hmmm. If the simplest solution is not idiomatic then the idiom is what's wanting not the solution, wouldn't you say? Unless there is a better explanation for why I should use the convoluted toysField and then toys and then set(value)

– salyela
Nov 27 '18 at 18:30

add a comment |

I saw that you already have found solution that satisfy you, but maybe you can consider this one:

class Cat(toys: Int = 3, val type: String) : Animal() {



    var toys = toys

        private set



    fun addQuota() {

        toys += 4

    }



}

answered Nov 29 '18 at 15:47

anber

1,41932550

I like this one, except it doesn't work for data class

– salyela
Nov 29 '18 at 20:06

I believe the only difference between data class and usual that data class have inbuilt toString and equals methods, which you can generate via IDE. Moreover Animal class also can't be data class

– anber
Nov 30 '18 at 7:11

Try it with room without data. Android studio still complains.

– salyela
Nov 30 '18 at 21:00

add a comment |

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3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

You can do this by using the property of the constructor as backing field for the toys property:

data class Cat(val type: String, private var toysField: Int = 3 ):Animal(){



    var toys = toysField

    private set(value){

        toysField = value

    }



    fun addQuota(){toys += 4}



}



abstract class Animal

I hope this works with room.

Source https://discuss.kotlinlang.org/t/private-setter-for-var-in-primary-constructor/3640/10

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

thanks for replying. Your answer should definitely work, but I found a simpler solution, which I am providing as an answer as well. Thanks! +1

– salyela
Nov 26 '18 at 23:48

I finally got a chance to test this code and it actually doesn't work. Here is the version that works: var toys = toysField *n*/ private set(value){ *n*/ toysField = value *n*/ } *n*/ get()=toysField

– salyela
Nov 30 '18 at 20:50

What part does not work and how does adding the getter change that?

– leonardkraemer
Nov 30 '18 at 21:03

add a comment |

You can do this by using the property of the constructor as backing field for the toys property:

data class Cat(val type: String, private var toysField: Int = 3 ):Animal(){



    var toys = toysField

    private set(value){

        toysField = value

    }



    fun addQuota(){toys += 4}



}



abstract class Animal

I hope this works with room.

Source https://discuss.kotlinlang.org/t/private-setter-for-var-in-primary-constructor/3640/10

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

thanks for replying. Your answer should definitely work, but I found a simpler solution, which I am providing as an answer as well. Thanks! +1

– salyela
Nov 26 '18 at 23:48

I finally got a chance to test this code and it actually doesn't work. Here is the version that works: var toys = toysField *n*/ private set(value){ *n*/ toysField = value *n*/ } *n*/ get()=toysField

– salyela
Nov 30 '18 at 20:50

What part does not work and how does adding the getter change that?

– leonardkraemer
Nov 30 '18 at 21:03

add a comment |

You can do this by using the property of the constructor as backing field for the toys property:

data class Cat(val type: String, private var toysField: Int = 3 ):Animal(){



    var toys = toysField

    private set(value){

        toysField = value

    }



    fun addQuota(){toys += 4}



}



abstract class Animal

I hope this works with room.

Source https://discuss.kotlinlang.org/t/private-setter-for-var-in-primary-constructor/3640/10

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

You can do this by using the property of the constructor as backing field for the toys property:

data class Cat(val type: String, private var toysField: Int = 3 ):Animal(){



    var toys = toysField

    private set(value){

        toysField = value

    }



    fun addQuota(){toys += 4}



}



abstract class Animal

I hope this works with room.

Source https://discuss.kotlinlang.org/t/private-setter-for-var-in-primary-constructor/3640/10

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

answered Nov 26 '18 at 21:32

leonardkraemer

3,60011634

thanks for replying. Your answer should definitely work, but I found a simpler solution, which I am providing as an answer as well. Thanks! +1

– salyela
Nov 26 '18 at 23:48

I finally got a chance to test this code and it actually doesn't work. Here is the version that works: var toys = toysField *n*/ private set(value){ *n*/ toysField = value *n*/ } *n*/ get()=toysField

– salyela
Nov 30 '18 at 20:50

What part does not work and how does adding the getter change that?

– leonardkraemer
Nov 30 '18 at 21:03

add a comment |

thanks for replying. Your answer should definitely work, but I found a simpler solution, which I am providing as an answer as well. Thanks! +1

– salyela
Nov 26 '18 at 23:48

I finally got a chance to test this code and it actually doesn't work. Here is the version that works: var toys = toysField *n*/ private set(value){ *n*/ toysField = value *n*/ } *n*/ get()=toysField

– salyela
Nov 30 '18 at 20:50

What part does not work and how does adding the getter change that?

– leonardkraemer
Nov 30 '18 at 21:03

thanks for replying. Your answer should definitely work, but I found a simpler solution, which I am providing as an answer as well. Thanks! +1

– salyela
Nov 26 '18 at 23:48

I finally got a chance to test this code and it actually doesn't work. Here is the version that works: var toys = toysField *n*/ private set(value){ *n*/ toysField = value *n*/ } *n*/ get()=toysField

– salyela
Nov 30 '18 at 20:50

What part does not work and how does adding the getter change that?

– leonardkraemer
Nov 30 '18 at 21:03

add a comment |

It turns out the following works:

data class Cat(private var toys:Int=3, val type:String):Animal(){

    ...

    fun getToys()=toys

}

answered Nov 26 '18 at 23:19

salyela

698

it works, but it's not really idiomatic. the solution with private set is preferred

– Lovis
Nov 27 '18 at 12:59

Hmmm. If the simplest solution is not idiomatic then the idiom is what's wanting not the solution, wouldn't you say? Unless there is a better explanation for why I should use the convoluted toysField and then toys and then set(value)

– salyela
Nov 27 '18 at 18:30

add a comment |

It turns out the following works:

data class Cat(private var toys:Int=3, val type:String):Animal(){

    ...

    fun getToys()=toys

}

answered Nov 26 '18 at 23:19

salyela

698

it works, but it's not really idiomatic. the solution with private set is preferred

– Lovis
Nov 27 '18 at 12:59

Hmmm. If the simplest solution is not idiomatic then the idiom is what's wanting not the solution, wouldn't you say? Unless there is a better explanation for why I should use the convoluted toysField and then toys and then set(value)

– salyela
Nov 27 '18 at 18:30

add a comment |

It turns out the following works:

data class Cat(private var toys:Int=3, val type:String):Animal(){

    ...

    fun getToys()=toys

}

answered Nov 26 '18 at 23:19

salyela

698

It turns out the following works:

data class Cat(private var toys:Int=3, val type:String):Animal(){

    ...

    fun getToys()=toys

}

answered Nov 26 '18 at 23:19

salyela

698

answered Nov 26 '18 at 23:19

salyela

698

answered Nov 26 '18 at 23:19

salyela

698

answered Nov 26 '18 at 23:19

salyela

698

it works, but it's not really idiomatic. the solution with private set is preferred

– Lovis
Nov 27 '18 at 12:59

Hmmm. If the simplest solution is not idiomatic then the idiom is what's wanting not the solution, wouldn't you say? Unless there is a better explanation for why I should use the convoluted toysField and then toys and then set(value)

– salyela
Nov 27 '18 at 18:30

add a comment |

it works, but it's not really idiomatic. the solution with private set is preferred

– Lovis
Nov 27 '18 at 12:59

Hmmm. If the simplest solution is not idiomatic then the idiom is what's wanting not the solution, wouldn't you say? Unless there is a better explanation for why I should use the convoluted toysField and then toys and then set(value)

– salyela
Nov 27 '18 at 18:30

it works, but it's not really idiomatic. the solution with private set is preferred

– Lovis
Nov 27 '18 at 12:59

Hmmm. If the simplest solution is not idiomatic then the idiom is what's wanting not the solution, wouldn't you say? Unless there is a better explanation for why I should use the convoluted toysField and then toys and then set(value)

– salyela
Nov 27 '18 at 18:30

add a comment |

I saw that you already have found solution that satisfy you, but maybe you can consider this one:

class Cat(toys: Int = 3, val type: String) : Animal() {



    var toys = toys

        private set



    fun addQuota() {

        toys += 4

    }



}

answered Nov 29 '18 at 15:47

anber

1,41932550

I like this one, except it doesn't work for data class

– salyela
Nov 29 '18 at 20:06

I believe the only difference between data class and usual that data class have inbuilt toString and equals methods, which you can generate via IDE. Moreover Animal class also can't be data class

– anber
Nov 30 '18 at 7:11

Try it with room without data. Android studio still complains.

– salyela
Nov 30 '18 at 21:00

add a comment |

I saw that you already have found solution that satisfy you, but maybe you can consider this one:

class Cat(toys: Int = 3, val type: String) : Animal() {



    var toys = toys

        private set



    fun addQuota() {

        toys += 4

    }



}

answered Nov 29 '18 at 15:47

anber

1,41932550

I like this one, except it doesn't work for data class

– salyela
Nov 29 '18 at 20:06

I believe the only difference between data class and usual that data class have inbuilt toString and equals methods, which you can generate via IDE. Moreover Animal class also can't be data class

– anber
Nov 30 '18 at 7:11

Try it with room without data. Android studio still complains.

– salyela
Nov 30 '18 at 21:00

add a comment |

I saw that you already have found solution that satisfy you, but maybe you can consider this one:

class Cat(toys: Int = 3, val type: String) : Animal() {



    var toys = toys

        private set



    fun addQuota() {

        toys += 4

    }



}

answered Nov 29 '18 at 15:47

anber

1,41932550

I saw that you already have found solution that satisfy you, but maybe you can consider this one:

class Cat(toys: Int = 3, val type: String) : Animal() {



    var toys = toys

        private set



    fun addQuota() {

        toys += 4

    }



}

answered Nov 29 '18 at 15:47

anber

1,41932550

answered Nov 29 '18 at 15:47

anber

1,41932550

answered Nov 29 '18 at 15:47

anber

1,41932550

answered Nov 29 '18 at 15:47

anber

1,41932550

I like this one, except it doesn't work for data class

– salyela
Nov 29 '18 at 20:06

I believe the only difference between data class and usual that data class have inbuilt toString and equals methods, which you can generate via IDE. Moreover Animal class also can't be data class

– anber
Nov 30 '18 at 7:11

Try it with room without data. Android studio still complains.

– salyela
Nov 30 '18 at 21:00

add a comment |

I like this one, except it doesn't work for data class

– salyela
Nov 29 '18 at 20:06

I believe the only difference between data class and usual that data class have inbuilt toString and equals methods, which you can generate via IDE. Moreover Animal class also can't be data class

– anber
Nov 30 '18 at 7:11

Try it with room without data. Android studio still complains.

– salyela
Nov 30 '18 at 21:00

I like this one, except it doesn't work for data class

– salyela
Nov 29 '18 at 20:06

I believe the only difference between data class and usual that data class have inbuilt toString and equals methods, which you can generate via IDE. Moreover Animal class also can't be data class

– anber
Nov 30 '18 at 7:11

Try it with room without data. Android studio still complains.

– salyela
Nov 30 '18 at 21:00

add a comment |

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