如何使用可变数据源在表视图中按字母顺序排列节标题

I store strings of a view controller in a string array. I import this string array as a Data Source in my table view. This all works smoothly. But now I would like to sort the table view and add section headers. The section header should be from the alphabet, the rows of the meaning sections should be all strings from the array, starting with the letter of the section header.I store strings of a view controller in a strin