A modern programming language that makes developers happier.

kotlinlang

<@U0129FYHT54> Hi,  you don’t define aLiveData
```lateinit var aLiveData: LiveData&lt;List&lt;..&gt;&gt;
aLiveData = // define live data
val list = aLiveData.value```

thank you, of course I did define that in my code. The point to focus is why the line "val list = aLiveData.value" can cause crash

If you call `aLiveData.value` before you assign `aLiveData = ...` Then it'll be null and crash

If `aLiveData` isn't guaranteed to be initialized before you use it, you should make it nullable instead

`aLiveData = getListFromDb()`
yeah, thats right but in that case the " lateinit exception" will be presented not NPE? since there is no lateinit exception, so I think in my code the "getListFromDb()" return a null livedata? That seems unreasonable with the query:
```@Query("SELECT * FROM table")
fun getListFromDb(): LiveData&lt;List&lt;DataA&gt;&gt;```


Put a breakpoint and see what is happening