swift 如何优雅的判断String 是否为nil 或者空格

extension String{
    
    /// check string cellection is whiteSpace
    var isBlank : Bool{
        return allSatisfy({$0.isWhitespace})
    }
}


extension Optional where Wrapped == String{
    var isBlank : Bool{
        return self?.isBlank ?? true
    }
}

var title: String? = nil
title.isBlank            // true
title = ""               
title.isBlank            // true
title = "  \t  "               
title.isBlank            // true
title = "Hello"
title.isBlank            // false