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String interpolation produces a debug description for an optional value; did you mean to make this explicit?

Last updated at Posted at 2018-11-27

#過去に出会った警告メッセージとその対処方法備忘録
##環境

  • XCode
  • Swift4.2

##警告メッセージ
String interpolation produces a debug description for an optional value; did you mean to make this explicit?

##警告発生コード

var text:String? = nil
text = "hoge"
				
print("\(text)")//warning

##原因と対処方法
###原因
Optional型でwrapされている文字列を、wrapしたまま直接print出力しようとしたことが原因みたい
###対処方法
この場合は、unwrapしてから出力してあげることで解決した。

##対処済みコード1
強制unwrap

var text:String? = nil
text = "hoge"
				
print("\(text!)")

##対処済みコード2
冗長的だけど、明示的にunwrap

var text:String? = nil
text = "hoge"

if let text = text
{
    print("\(text)")
}
else
{
    print("nil")
}		

##対処済みコード3
??演算子を利用してtextがnilの時のデフォルト値を指定しても良い

var text:String? = nil
text = "hoge"
print("\(text ?? "text is nil")")

##対処済みコード4
Optionalそのままでいいから、警告を消したい時は以下のように記述する

var text:String? = nil
text = "hoge"
print("\(text as String?)")
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