In Go, new is used to assign primitive type or structure pointers and initialize to zero values, while make is dedicated to creating slices, maps, and channels that can be used directly. The specific differences are as follows: 1. new(T) allocates memory for type T and returns a pointer, which is suitable for basic types and structure initialization such as int and string; 2. make is used to create slices, maps, and chan, and at the same time completes internal structure initialization to ensure that the object can be used directly; 3. Struct{} can be used instead of new, which is more intuitive and concise; 4. Incorrect use will lead to inefficiency or runtime errors. If you use new to create slices, you will get nil value and need subsequent assignment, which will increase complexity.
In Go, make and new are keywords used to allocate memory, but their usage scenarios are completely different. Simply put:
-
new(T)is used to assign a zero value to type T and return a pointer to it. -
makeis specifically used to create slices, maps, and channels. It not only allocates memory, but also initializes internal structures.
Not knowing the difference between the two may lead to inefficiency or errors in the code. Let’s start from the actual purpose and see when to use which one.
new: Pointer and structure initialization suitable for basic types
The function of new is very simple, which is to allocate a default memory space to a certain type and return a pointer. for example:
p := new(int) fmt.Println(*p) // Output 0
This is useful when you need a pointer with an initial value of zero, especially when dealing with structures:
type User struct {
Name string
Age int
}
u := new(User)
u.Name = "Alice" This way you get a pointer to the User type, and all fields are initialized to their respective zero values.
Tip: Although you can also write
&User{}, the two are equivalent in most cases. However,newis more suitable for situations where you just want to get an empty structure pointer.
Make: specially created for slice, map, chan
make not only allocates memory, it also does some necessary initialization work to ensure that these types can be used directly. For example:
s := make([]int, 0, 5) // Create a slice with length 0 and capacity 5 m := make(map[string]int) // Create an empty map c := make(chan int) // Create an unbuffered channel
If you try to create these types with new , although there will be no syntax error, you will get a pointer to nil, and subsequent operations will have errors:
s := new([]int) fmt.Println(s == nil) // false, but *s is nil! *s = append(*s, 1) // It's OK to do this, but it's a bit troublesome
So, when you need a slice, map or chan that can be used directly, be sure to use make .
Use suggestions: Determine which one to use according to the type
To summarize, to determine whether to use make or new , you can refer to the following points:
- If you want to create a basic type or structure of pointer type , use
new - If you want to create slice, map or channel , use
makeregardless of whether there is an initial value or not - If you want to construct a structure with default values, you can use
&Struct{}instead ofnew
For example:
| Scene | Recommended method |
|---|---|
| Create an int pointer | new(int)
|
| Create a map | make(map[string]int)
|
| Initialize a structure pointer | new(MyStruct) or &MyStruct{}
|
| Create a slice with capacity | make([]int, 0, 10)
|
Basically that's it. Remember, new is a general memory allocator, and make is a constructor for a specific type (slice/map/chan). Using it correctly can make your code clearer and safer.
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