ios - 如何获取索引(:) to return multiple indices?

Question

这里是一个组数组。

var group = ["H","H","E","D",
             "G","D","G","E",
             "D","B","A","B",
             "A","A","G","C",
             "C","H","D","G",
             "H","B","E","F",
             "F","C","E","A",
             "B","C","F","F"]

我想做这样的事情来找到“A”的索引。

group.index(of: "A"!)

但这将只返回第一个索引，而不会返回接下来三个“A”的其他索引。

print(group.index(of: "A")!) //10

如何让程序返回“A”的所有四个索引？

Answer 1

您可以结合使用enumerated 和compactMap:

let indexArray = group.enumerated().compactMap {
   $0.element == "A" ? $0.offset : nil
}    
print(indexArray) // [10, 12, 13, 27]