英文:
Golang: Defensive interfaces for nil types
问题
最近我发现一些 Go 代码在一个测试框架中运行时存在一些未初始化的变量。
这导致了一个 panic，其中的堆栈跟踪在顶部包含了一些 C 代码。
在函数中，有没有一种简洁的方法可以检测被引用为实现成员的结构体是否为 nil？例如：
func (d *Dog) canBark() bool {
// 如果 d 是 nil，会抛出一个晦涩的异常。
// 有没有一种方法可以防止这种情况发生？
}
抛出的错误信息是：
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4ec83a]
goroutine 16 [running]:
runtime.panic(0x9b7400, 0xf7ddf3)
在 Go 中，这种底层错误似乎应该很少发生，甚至可能根本不会发生...
可能有一种 Golang 的方式来处理不会在代码中过多使用 if/else 逻辑的 nil 引用。例如，在 Java 中，你可以在一个空指针异常处理程序中包装一个大的代码段。
英文:
I recently found some go code was running in a test framework where there were some uninitialized variables.
This lead to a panic, which had a stack trace containing some c code at the top.
Is there a way, in functions, that we can concisely detect wether the struct which is referenced as the implementing member is nil? i.e.
func ( d *Dog ) canBark Bool {
//if d is nil, cryptic exception is thrown.
//is there a way to defend against this?
}
The error which is thrown is
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4ec83a]
goroutine 16 [running]:
runtime.panic(0x9b7400, 0xf7ddf3)
It seems that in go, such lower level errors should occur very rarely, maybe never at all...
There might be a Golang way to deal with nil references which don't clutter the code too much with if/else logic. For example, in java, you can wrap a large code segment in a null pointer exception handler.
答案1
得分: 4
你可以检查是否为nil，然后执行相应的操作：
func (d *Dog) canBark() bool {
if d == nil {
// 做一些有用的事情，比如记录用于以后调试的堆栈跟踪
log.Print("尝试让一个空的狗叫！")
return false
}
// 执行常规操作
}
这段代码是一个示例，用于检查一个Dog对象是否为nil，如果是，则打印一条日志并返回false。否则，执行正常的操作。
英文:
You can check for nil and then do whatever:
func (d *Dog) canBark bool {
if d == nil {
// do something useful, maybe? Like log
// a stack trace for debugging later
log.Print("Attempt to bark a nil dog!")
return false
}
// do the regular things
}
答案2
得分: 2
func (d *Dog) bool {
if d == nil {
// 一个空的狗不能叫
return false
}
}
在Go语言中，完全可以在空的结构体上使用方法。然而，对于空的接口来说就不同了。你无法防止这种情况发生，因为没有类型可以调用方法。
type Barker interface {
CanBark() bool
}
var dog Barker
// 报错
dog.CanBark()
在Go语言中，如果不正确地初始化数据结构，或者方法出现问题，都会导致编程错误。如果一个类型的值从函数或方法中返回给你，通常也会返回一个错误值，指示第一个值是否可以使用。
英文:
Sure:
func ( d *Dog ) bool {
if d == nil {
// a nil dog can't bark
return false
}
}
It's entirely possible to use methods on a nil struct. However, a nil interface is another story. You can't defend against that, because there's no type to call a method on.
type Barker interface {
CanBark() bool
}
var dog Barker
//panics
dog.CanBark()
In go, it's a programming error to improperly initialize a data structure, and methods can panic. If a type value is returned to you from a function or a method, there is generally an error value returned as well indicating whether the first value can be used.
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