英文:
Handle nil in loop from list Golang
问题
我正在循环遍历从后端接收到的一些数据，其中可能包含一个空值，在程序中会出现“panic: runtime error: invalid memory address or nil pointer dereference”错误。
我该如何处理空值？我想将空值设置为“EMPTY”。
我尝试了以下代码，但仍然会出错：
for _, res := range resp.Autombiles {
for _, trk := range res.Trucks {
if trk == nil {
println("EMPTY")
} else {
println(*trk.EngineType)
}
}
}
}
这是我的循环代码：
for _, res := range resp.Autombiles {
for _, trk := range res.Trucks {
fmt.Println(*trk.EngineType)
}
}
}
英文:
I'm looping through some data received from a backend and might contain a nil in the middle, the program crashes with panic: runtime error: invalid memory address or nil pointer dereference
How can i handle the nil? Would like to set an nil to show "EMPTY"
I've tried this but still crashes:
for _, res := range resp.Autombiles {
for _, trk := range res.Trucks {
if trk == nil {
println("EMPTY")
} else {
println(*trk.EngineType)
}
}
}
}
Here's my loop:
for _, res := range resp.Autombiles {
for _, trk := range res.Trucks {
fmt.Println(*trk.EngineType)
}
}
}
答案1
得分: 1
看起来res.Trucks是空的。所以在创建trk变量之前，你的程序会崩溃，就在这里：for _, res := range res.Trucks{}
for _, res := range resp.Autombiles {
// res.Trucks 可能为空
for _, trk := range res.Trucks {
...
}
}
所以，在res.Trucks存在的情况下添加一个检查：
for _, res := range resp.Autombiles {
if res.Trucks != nil {
for _, trk := range res.Trucks {
if trk == nil || trk.EngineType == nil {
println("EMPTY")
} else {
println(*trk.EngineType)
}
}
}
}
英文:
Looks like res.Trucks is nil. So your program crashes before trk variable is created, here. for _, res := range res.Trucks{}
for _, res := range resp.Autombiles {
// res.Trucks can be nil
for _, trk := range res.Trucks {
...
}
}
So, add a check for existance of res.Trucks
for _, res := range resp.Autombiles {
if res.Trucks != nil {
for _, trk := range res.Trucks {
if trk == nil || trk.EngineType == nil {
println("EMPTY")
} else {
println(*trk.EngineType)
}
}
}
}
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