Kotlin空安全空类型浅谈

// name为不可为空的变量， 不能赋值为null ，若有判断 if(name==null) 无意义，因为肯定不为null
var name : String = ""
// role 为可空变量
var role : String? = ""

        var name : String ?= ""
        if (name == null){
            Log.i(Tag,"name==null")
        }else{
            Log.i(Tag, "name!=null")
        }

        var name : String ?= "abc"
        Log.i(Tag,"name="+name?.length)

var name:String?="abc"

fun getNameLength():String?{
      return name
}

    fun logUnNullList(arr:Array<String>):Unit{
        for (item in arr){
            if (arr==null){
                continue
            }else{
                Log.i(Tag,"非空元素为->"+item)
            }
        }
    }

    fun logUnNullList(arr:Array<String>):Unit{
        for (item in arr){
            item?.let {Log.i(Tag,"非空元素为->"+item)  }
        }
    }

var name:String?="abc"
var nameLength:Int = 0
nameLength = name?.length?:-1  // 取name的length ，若name为null,则nameLength的值为-1

var name:String?=null
nameLength = name!!.length

var name:String?= 12 as String

var name:String?= 12 as? String
Log.i(Tag,"name="+ name)
// 打印日志： name=null