this@MainActivity vs MainActivity@this in kotlin

Question

As you may see that

this@MainActivity or MainActivity@this

is valid while starting activity in kotlin. I tried to find out answer but I did not found anything. Can anyone know about exact difference of it and which one valid ? Why it allowed both ?

`MainActivity@this` not valid in my side – John Joe Jan 09 '19 at 08:25 — John Joe, Jan 09 '19 at 08:25

score 9 · Accepted Answer · answered Jan 09 '19 at 08:30

9

According to Kotlin's Grammar documentation,

MainActivity@this is just a label for this with the name "MainActivity". You can set whatever label you want.

this@MainActivity is an actual reference of this from MainActivity

Hope I make it clear.

answered Jan 09 '19 at 08:30

Ye Min Htut

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Thank you. Intent(this@MainActivity, SettingActivity::class.java) and Intent(MainActivity@this, SettingActivity::class.java) both are valid and working fine. Is there any reason or what statement is same as MainActivity.class and this within MainActivity. – Smeet Jan 10 '19 at 05:17
You might want to read about it here https://stackoverflow.com/questions/3434041/meaning-of-this-and-class-in-java?lq=1 – Ye Min Htut Jan 10 '19 at 07:40

score 4 · Answer 2 · answered Jan 09 '19 at 08:30

4

this@MainActivity - it is a reference to current MainActivity instance.

MainActivity@this - it is definition of a name of the label, i.e. MainActivity.

More info about labels.

answered Jan 09 '19 at 08:30

Sergio

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this@MainActivity vs MainActivity@this in kotlin

2 Answers2