php小编鱼仔为您揭示一个关于切片的问题：为什么通过通道和 goroutine 写入切片最终为空？在Go语言中，通道和 goroutine 是并发编程的重要工具，但在某些情况下，使用它们写入切片可能会出现意外结果。本文将详细解释这个问题的原因，并提供解决方案，帮助您更好地理解和处理这种情况。
问题内容
我运行这个函数：
func run() () {
// this slice is going to be filled out by a channel and goroutine.
vertices := make([]vertex, 0)
var wg sync.waitgroup
// obtain a writer to fill out the vertices.
writer := writer(&wg, vertices)
// run an arbitrary logic to send data to writer.
logic(writer)
// stop the writer reading on the channel.
close(writer)
// wait for the write to complete.
wg.wait()
// see if vertices slice is actually filled out.
doublecheckvertices(vertices)
}
但最终，我的 vertices 切片是空的：
func doublecheckvertices(vertices []vertex) () {
// here i notice that `vertices` slice is actually empty :(
}
返回 writer 的函数是这样的：
func writer(wg *sync.waitgroup, vertices []vertex) (chan<- []*triangle3) {
// external code writes to this channel.
// this goroutine reads the channel and writes to vertices.
writer := make(chan []*triangle3)
// write by a goroutine.
wg.add(1)
go func() {
defer wg.done()
a := vertex{}
// read from the channel and write them to vertices.
for ts := range writer {
for _, t := range ts {
a.x = float32(t.v[0].x)
a.y = float32(t.v[0].y)
a.z = float32(t.v[0].z)
vertices = append(vertices, a)
}
}
}()
return writer
}
任何人都可以帮我弄清楚为什么我的 vertices 切片最终是空的吗？
日志
日志表明 vertices 切片实际上已填充。但由于某种原因，传递给doublecheckvertices时为空。
vertices = append(vertices, a)
// This Log shows the slice is actually filled out:
fmt.Printf("vertices len() is %v\n", len(vertices))
解决方法
这看起来类似于“将切片作为函数参数传递，并修改原始切片”
如果您希望 goroutine 修改您在外部创建的切片，则需要一个指向该切片的指针：
func Writer(wg *sync.WaitGroup, vertices *[]Vertex) (chan<- []*Triangle3) {
// External code writes to this channel.
// This goroutine reads the channel and writes to vertices.
writer := make(chan []*Triangle3)
// Write by a goroutine.
wg.Add(1)
go func() {
defer wg.Done()
a := Vertex{}
// Read from the channel and write them to vertices.
for ts := range writer {
for _, t := range ts {
a.X = float32(t.V[0].X)
a.Y = float32(t.V[0].Y)
a.Z = float32(t.V[0].Z)
*vertices = append(*vertices, a) <=====
}
}
}()
return writer
}
