๐ฑ dreaming DiNO
[Kotlin] ๊ธฐ๋ณธ๋ฌธ๋ฒ-1 ๋ณธ๋ฌธ
// letํจ์์ ์ฌ์ฉ๋ฒ -> if (null X) ์์ ๋๋ค์ ์คํํด๋ผ!
val email : String?= "mia@naver.com"
email?.let {
println("My email is ${email}")
}
NunNull -> something ์ผ๋ก ์ด๊ธฐํ
null ์ด๋ผ ์์ letํจ์ ๋๋ค์์ด ์์ ์คํ์ด ์๋์ ์๋ฌด ๋ฐ์์ด ์๋๊ฒ! (ํด๊ฒฐ^ใ ^)
fun let(){
// ? ์ฌ์ฉ๋ฒ
var name : String? = "mia" // null์ด๋ฉด mia๋ก ์ด๊ธฐํ
name?.let{
println(it)
}
// for๋ฌธ ์ฌ์ฉ๋ฒ
val students = arrayListOf("mia", "jino", "ted", "hoxvi")
for (name in students) {
println("${name}")
}
// ?: ์๋น์คํ๋ ์ฌ๋ฆฌ ใ
null์ด๋ผ๋ฉด default ๊ฐ ์ ์
val lastName : String? = null
val fullName = name + " " + (lastName?:"No lastName")
println(fullName)
}
// !! ์ฌ์ฉ๋ฒ -> null์ด ์๋์ ํ์ ํ ๋ (์ง์ํ๋ ํธ)
fun ignoreNull(str : String){
val notNull : String = str!!
val upper = notNull.toUpperCase()
val notNull2 : String? = str!!
val upper2 = notNull2.toUpperCase() // Error
// letํจ์์ ์ฌ์ฉ๋ฒ -> if (null X) ์์ ๋๋ค์ ์คํํด๋ผ!
val email : String?= "mia@naver.com"
email?.let {
println("My email is ${email}")
}
๋ง์ฝ email์ด null์ด๋ฉด letํจ์๋ ์คํ๋์ง ์์ = ๋๋ค์ ์คํX
'Android' ์นดํ ๊ณ ๋ฆฌ์ ๋ค๋ฅธ ๊ธ
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