Kotlin : Create extension function file?plus

Question

I am developing some lib in Kotlin, I am not finding this solution,

How can I resolve this issue, It's saying that create extension function File?.plus, In java it works fine but in Kotlin how to write this code?

Please not just copy a screenshot into the issue if possible but provide the sourcecode. — guenhter, Aug 22 '17 at 11:34
@MohitSuthar - but it doesn't encourage people to help. Please use text for code rather than screenshots. — Les, Aug 22 '17 at 11:43

score 6 · Answer 1 · answered Aug 22 '17 at 11:50

6

You don't need to invent more code, just change the plus (+) to a comma(,).

val sdcard = File(Environment.getExternalStorageDirectory(), "/PicTaker/Images")

answered Aug 22 '17 at 11:50

Les

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guenhter · Accepted Answer · 2017-08-22T11:50:20.650

5

You have three options:

1) Avoid that you concat a File with a String by calling the toString() what results in concating two strings.

val sdCard = File(Environment.getExternalStorageDirectory().toString() + "/PicTaker/Images")

2) Write that extension-function and return a string

private operator fun File?.plus(s: String): String {
    return this.toString() + s
}

3) Use string template

val sdCard = File("${Environment.getExternalStorageDirectory()}/PicTaker/Image‌s")

edited Aug 22 '17 at 11:50

answered Aug 22 '17 at 11:40

guenhter

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String template also works. `"${Environment.getExternalStorageDirectory()}/PicTaker/Images"` – BakaWaii Aug 22 '17 at 11:48
@BakaWaii great third option. I add this one in this post. thx – guenhter Aug 22 '17 at 11:49

score 3 · Answer 3 · answered Aug 22 '17 at 11:39

Add toString():

val sdcard = File(Environment.getExternalStorageDirectory().toString() + "...")

In Kotlin, we can do operator overloading for + and Kotlin compiler thinks you are trying to use the overloaded plus operator for File? type. And provides an option to create the extension function to File?

Kotlin : Create extension function file?plus

3 Answers3