If I have a top level object declaration
package com.example
object MyObject {}
how can I convert the string com.example.MyObject into a reference to MyObject?
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3 Answers
If you have kotlin-reflect on the classpath then you can use the objectInstance property of KClass
fun main(args: Array<String>) {
val fqn = "com.example.MyObject"
val clz: Class<*> = Class.forName(fqn)
val instance = clz.kotlin.objectInstance
println(instance) // com.example.MyObject@71623278
}
if you don't have kotlin-reflect then you can do it in a plain old java-way
fun main(args: Array<String>) {
val fqn = "com.example.MyObject"
val clz: Class<*> = Class.forName(fqn)
val field: Field = clz.getDeclaredField("INSTANCE")
val instance = field.get(null)
println(instance) // com.example.MyObject@76ed5528
}
answered Jun 20, 2017 at 8:31
Sergey Tselovalnikov
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2 Comments
fralbo
considering we use a function to return an object instance from its name, what is the return type please?
Alexey Romanov
@fralbo
Any would be the only reasonable return type in general (or Any? if you want to return null when there's no such object).you can using kotlin reflection, for example:
val it = Class.forName("com.example.MyObject").kotlin.objectInstance as MyObject;
3 Comments
Alexey Romanov
If you can do
as MyObject, you can write MyObject instead of all this in the first place :)
Mikolasan
@AlexeyRomanov But what if the string represents subclass and
as MyObject casts it to a base class. Anyway, you can throw out as MyObject and consider this example as a good one-liner.Alexey Romanov
"But what if the string represents subclass and
as MyObject casts it to a base class" Doesn't apply to this question, where MyObject is an object which can't be extended. "you can throw out as MyObject" Yes, I agree.Same a java code, you need use Class.forName("com.example.MyObject"). Now you have a Java class, but using kotlin extension, it convert to Kotlin class. Class.forName("com.example.MyObject").kotlin
