我有一个函数，它接受Article和以Article为接收器的可为null的方法。我想调用可为null的方法，并仅在它存在的情况下返回其结果。我该怎么做？
fun foo(article: Article, method: (Article.() -> String)? = null): String? =
article?.method() // how can I do this?
fun foo(article: Article, method: (Article.() -> String)? = null): String? =
method?.invoke(article)
或
fun foo(article: Article, method: (Article.() -> String)? = null): String? =
method?.let { article.it() }