I sometimes see statements like somevariable.value?.add() What purpose does the question mark serve?
(Sorry, at the time of post I had no idea this was Kotlin, I thought it was java)
I sometimes see statements like somevariable.value?.add() What purpose does the question mark serve?
(Sorry, at the time of post I had no idea this was Kotlin, I thought it was java)
Kotlin treats null as something more than the source of null-pointer exceptions.
在您的代码片段中，somevariable.value是"可空类型"，例如MutableList?或Axolotl?.MutableList不能是null，但MutableList?可能是null.
通常，要在对象上调用函数，需要使用..
对变量、参数或属性调用函数的一个选项
null, your function call is ignored, and null is the
resultnull，则函数调用将正常进行So, in your case:
如果somevariable.value是null，则跳过add()呼叫
如果somevariable.value不是null，则对somevariable.value进行add()调用