如果长度> 100，则删除切片中的第一项

Question

When the RSS feeds updates (it doesn't right now, just dummy data) the new items are appended to the "feed" slice. Over time this could mean that it contains millions of items, I don't want that.

So when there are more than 100 items in the slice it should delete items starting from the top (item 0). In this example I'm using an RSS file with ust 100 items so the sample code below should delete from the top after 50 items:

package main

import (
    "fmt"
    "github.com/SlyMarbo/rss"
    "time"
)

var feed *rss.Feed
var directory = "./dump"

func main() {
    for {
        checkRSS()
        // Check every minute if feed.Refresh has passed so it run's update()
        time.Sleep(1 * time.Minute)
    }
}

func checkRSS() (*rss.Feed, error) {
    var err error
    // If feed is still empty fetch it first so we can run update()
    if feed == nil {
        feed, err = rss.Fetch("http://cloud.dgier.nl/api.xml")
    } else {
        err = feed.Update()
    }
    length := len(feed.Items)
    for key, value := range feed.Items {
        fmt.Println(key, value.Title, value.Read)
        if key >= 50 {
            fmt.Println("Item key is > 50")

        }
    }
    fmt.Printf("Current length: %d
", length)
    fmt.Printf("Refreshing at %s
", feed.Refresh)
    return feed, err
}

Answer 1

To achieve this you probably want to use subslicing. Say you want to remove x items from feed, you can simply do feed = feed[x:] which will yield all items after index x-1 and assign it back to the feed slice. If in your actual code you just want to remove the first item then it would be feed = feed[1:]