In Go, whether to use pointers depends on whether the original variable, structure size and code readability need to be modified. 1. If the function needs to modify the original structure or structure is larger (such as more than a few hundred bytes), the pointer should be passed to avoid copy overhead; otherwise, the value transmission is safer and more intuitive. 2. If the method needs to modify the receiver status or the structure is large, the pointer receiver should be used; otherwise, the value receiver is available because it supports the call of pointers and values. 3. It is recommended to use pointers to improve performance when large structures are frequently transmitted, while small structures are more efficient and clear in value transmission. 4. It is safer to pass value without side effects, and pointers are suitable for shared data modification. The selection basis includes: whether to modify the original data, structure size, and code clarity.
In Go language, using pointers or values directly affects the performance, readability and behavior of the program. Simply put: if you want the function to modify the variable itself, or the structure is larger, you should use pointers; otherwise, it is safer and more intuitive to use values.
The following is a few common scenarios to talk about the differences and selection basis of the two.
Function parameter passing: value passing vs pointer passing
All parameter passing in Go are "value passing". That is, the function receives a copy of the original data.
- Passing value : Modification of the structure inside the function will not affect the outside.
- Passing pointer : The function can modify the content of the original variable.
For example:
type User struct {
Name string
}
func changeName(u User) {
u.Name = "Tom"
}
func changeNamePtr(u *User) {
u.Name = "Jerry"
} Calling changeName(user) will not change the outside user.Name , but using changeNamePtr(&user) will take effect.
so:
- If you just need to read the structure content, there is no problem passing the value.
- If you need to modify the original structure, or the structure is large (such as more than a few hundred bytes), it is recommended to pass pointers to avoid copy overhead.
Method Set: Pointer Receiver vs Value Receiver
When defining a method in Go, you can choose whether the receiver is a value or a pointer:
func (u User) SayHi() {}
func (u *User) ChangeName(newName string) {}Here is a key point:
- The method of the value recipient can be called by the value and pointer (Go automatically handles it).
- The method of the pointer receiver can only be called by the pointer, not by the value.
Another point: If you want to modify the field of the receiver itself through methods, you must use a pointer to the receiver. Otherwise, the copy will be changed.
so:
- If the method does not need to modify the receiver status, you can use the value of the receiver.
- If the method wants to modify the receiver content, or the structure is large, it is recommended to use a pointer to the receiver.
Performance considerations: Structural size determines whether to use pointers
When you frequently pass a larger structure (such as containing multiple fields or nested structures), using value passes will cause a large amount of memory replication and affect performance.
for example:
type BigStruct struct {
Data [1024]byte
}When this structure is used as a parameter or return value, if passed with a value, 1KB of data will be copied each time. If it is called frequently, resources will be wasted.
suggestion:
- When the structure is larger than a few dozen bytes, try to use a pointer.
- For small structures (such as only one or two fields), value passing is faster and clearer.
Readability and security: Values are "cleaner" than pointers
One advantage of using values is that you don't have to worry about side effects. Because it is a copy, no matter how much it is tossed with a function or method, it will not affect the outside.
Pointer operation may bring unexpected modifications and increase understanding costs.
so:
- If you don't want functions/methods to have an impact on the outside, it's safer to use values.
- If you explicitly want to share data, it is more appropriate to use pointers.
Basically that's it. Selecting a pointer or a value depends on whether you want to modify the original data, structure size, and code clarity. It is not complicated but it is easy to ignore details. Just pay more attention when writing.
The above is the detailed content of Golang pointer vs value explained. For more information, please follow other related articles on the PHP Chinese website!
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