how to read first 5 lines of csv file using built in ruby csv

Question

My application lets user to upload csv file with maximum of 50MB. I wanted to show the user the preview of the uploaded file. Can I read only the first 5 lines of csv? I am currently using CSV.read function, obviously this will read the entire file and is slow.

Answer 1

CSV#foreach返回一个可枚举的，因此只需对其调用Enumerable#take ：

csv_preview_data = CSV.foreach(csv_path, headers: false).take(5)

Answer 2

我认为读取固定数量记录的最简单方法是：

preview_data = CSV.readlines(csv_path, headers: false)[0,5]