How to check if a lateinit variable has been initialized

Question

I wonder if there is a way to check if a lateinit variable has been initialized  For example   class Foo          private lateinit var myFile  File      fun bar path  String             path  let   myFile   File it               fun bar2             myFile whateverMethod              May crash since I don t know whether myFile has been initialized

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Accepted answer gives me a compiler error in Kotlin 1 3   I had to explicitly mention the this keyword before     Below is the working code   lateinit var file  File  if  this  file isInitialized            file is not null

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You can easily do this by    variableName isInitialized  or this  variableName isInitialized  But if you are inside a listener or inner class  do this  this OuterClassName  variableName isInitialized  Note  The above statements work fine if you are writing them in the same file same class or inner class  where the variable is declared but this will not work if you want to check the variable of other class  which could be a superclass or any other class which is instantiated   for ex  class Test       lateinit var str String    And to check if str is initialized   What we are doing here  checking isInitialized for field str of Test class in Test2 class  And we get an error backing field of var is not accessible at this point  Check a question already raised about this

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To check if a lateinit var were initialised or not use a  isInitialized on the reference to that property   if  foo  bar isInitialized        println foo bar         This checking is only available for the properties that are accessible lexically  i e  declared in the same type or in one of the outer types  or at top level in the same file

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If you have a lateinit property in one class and need to check if it is initialized from another class if foo  file isInitialized     this wouldn t work  The workaround I have found is to create a function to check if the property is initialized and then you can call that function from any other class  Example  class Foo          private lateinit var myFile  File      fun isFileInitialised       file isInitialized        in another class class Bar          val foo   Foo        if foo isFileInitialised       this should work

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Using  isInitialized property one can check initialization state of a lateinit variable  if    file isInitialized           File is initialized   else          File is not initialized

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kotlin UninitializedPropertyAccessException  lateinit property clientKeypair has not been initialized   Bytecode says   blah blah    public final static synthetic access getClientKeypair p Lcom takharsh ecdh MainActivity  Ljava security KeyPair    L0 LINENUMBER 11 L0 ALOAD 0 GETFIELD com takharsh ecdh MainActivity clientKeypair   Ljava security KeyPair  DUP IFNONNULL L1 LDC  clientKeypair  INVOKESTATIC kotlin jvm internal Intrinsics throwUninitializedPropertyAccessException  Ljava lang String  V     L1 ARETURN   L2     LOCALVARIABLE  this Lcom takharsh ecdh MainActivity  L0 L2 0     MAXSTACK   2     MAXLOCALS   1  Kotlin creates an extra local variable of same instance and check if it null or not  if null then throws  throwUninitializedPropertyAccessException  else return the local object  Above bytecode explained here Solution Since kotlin 1 2 it allows to check weather lateinit var has been initialized or not using  isInitialized

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Try to use it and you will receive a UninitializedPropertyAccessException if it is not initialized   lateinit is specifically for cases where fields are initialized after construction  but before actual use  a model which most injection frameworks use   If this is not your use case lateinit might not be the right choice   EDIT  Based on what you want to do something like this would work better   val chosenFile   SimpleObjectProperty lt File  gt  val button  Button     Disables the button if chosenFile get   is null button disableProperty bind chosenFile isNull

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There is a lateinit improvement in Kotlin 1 2 that allows to check the initialization state of lateinit variable directly   lateinit var file  File      if  this  file isInitialized            See the annoucement on JetBrains blog or the KEEP proposal   UPDATE  Kotlin 1 2 has been released  You can find lateinit enhancements here    Checking whether a lateinit var is initialized Lateinit top-level properties and local variables

[kotlin] How to check if a "lateinit" variable has been initialized?

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