Can you add List<MyClass>example to README?

[NunciosChums]

I'm using Android Studio 3.0 + kotlin.

// build.gradle
compile "com.marcinmoskala.PreferenceHolder:preferenceholder:1.5"
compile "com.marcinmoskala.PreferenceHolder:preferenceholder-gson-serializer:1.5"

// class App : Application()
override fun onCreate() {
  super.onCreate()
  PreferenceHolder.setContext(applicationContext)
  PreferenceHolder.serializer = GsonSerializer(Gson())
}

class User(name: String, age: Int = 0) {
  var name: String? = name
  var age: Int? = age
}

object AppPreference : PreferenceHolder() {
  var users: List<User>? by bindToPreferenceFieldNullable()
}

// add 
val users: ArrayList<User> = ArrayList()
for (i in (0..5)) {
  users.add(User("name" + i, i))
}
AppPreference.users = users

// get
Log.i("###", AppPreference.users.toString()) 
// => [{age=0.0, name=name0}, {age=1.0, name=name1}, {age=2.0, name=name2}, {age=3.0, name=name3}, {age=4.0, name=name4}, {age=5.0, name=name5}]

for (user in AppPreference.users!!) {
  Log.i("@@@", user.name)
}
// => java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to kr.susemi99.testkotlin.model.User

val users = Gson().fromJson<List<User>>(AppPreference.users)
val users: List<User> = Gson().fromJson(AppPreference.users)
// => compile error

val usersType = object : TypeToken<List<User>>() {}.type
val users = Gson().fromJson<List<User>>(AppPreference.users, usersType)
// => compile error

Please add some more detailed instructions for beginners.

[MarcinMoskala]

I am checking this out, but my first comment, as a Kotlin teacher, is that you can optimize User and users creation:

class User(var name: String, var age: Int = 0)
val users = List(6) { i -> User("Name$i", i) }

[MarcinMoskala]

I cannot reproduce your problem. I've implemented tests for this case.

[{"age":0,"name":"Name0"},{"age":1,"name":"Name1"},{"age":2,"name":"Name2"},{"age":3,"name":"Name3"},{"age":4,"name":"Name4"},{"age":5,"name":"Name5"}]

Try to make two mentioned by my changes.

If you will still have this problem then place, give me more details. First of all, presented User class does not have a toString method implemented, so:

users.toString()

should produce something like this:

[com.marcinmoskala.kotlinpreferences.issue2test.Issue2Test$User@495824e, com.marcinmoskala.kotlinpreferences.issue2test.Issue2Test$User@7b06f6f, com.marcinmoskala.kotlinpreferences.issue2test.Issue2Test$User@6ed747c, com.marcinmoskala.kotlinpreferences.issue2test.Issue2Test$User@809105, com.marcinmoskala.kotlinpreferences.issue2test.Issue2Test$User@1cb755a, com.marcinmoskala.kotlinpreferences.issue2test.Issue2Test$User@efe938b]

Simple Kotlin solution is to use data modifier:

data class User(var name: String, var age: Int = 0)

Also Gson funcions are not working in my project. What Gson version are you using?

[NunciosChums]

I found something.

I changed User class like this

data class User(var name: String, var age: Int = 0)

and add

val users = List(5) { i -> User("Name$i", i) }
AppPreference.users = users
Log.i("###", "" + AppPreference.users)
// => [User(name=Name0, age=0), User(name=Name1, age=1), User(name=Name2, age=2), User(name=Name3, age=3), User(name=Name4, age=4)]

but after app restart

Log.i("###", "" + AppPreference.users)
// => [{age=0.0, name=Name0}, {age=1.0, name=Name1}, {age=2.0, name=Name2}, {age=3.0, name=Name3}, {age=4.0, name=Name4}]

This is my build.gradle

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:26.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    implementation 'com.marcinmoskala.PreferenceHolder:preferenceholder:1.5'
    implementation 'com.marcinmoskala.PreferenceHolder:preferenceholder-gson-serializer:1.5'
}

[MarcinMoskala]

This is quite wired. I would expect from toString something like this:
[User(name=Name0, age=0), ...]
And from GSON serializar:
[{"name"="Name0", "age"="0"}, ...]
Your string is neather of them.

Are you sure that you are saving the value before obteining it? Because otherwice you may still operate on some old data that were saved before. If you are not sure then please change AppPreference user property name or set come custom key.

[NunciosChums]

https://github.com/susemi99/TestKotlinPreference
here is my sample code.

[MarcinMoskala]

Your project is working perfectly fine in my env.

[NunciosChums]

Please watch this video.
https://youtu.be/l1I0jeNaVkw

[MarcinMoskala]

I am really sorry, you are right. I improved test so it is now checking presented case. I also fixed this problem in version 1.51

[MarcinMoskala]

And thank you for your contribution :)

[NunciosChums]

Thank you very much 👍