What type is golang new?

Golang is an increasingly popular programming language. During its rapid development, a common question is what type parameters should be provided when using the new keyword in Golang. This question is a bit tricky and requires a deep understanding of the type system in Golang and the nature of the new keyword.

First, let us review the new keyword in Golang. The new keyword is used to allocate memory space on the heap and return its address. Specifically, new accepts a type parameter and returns a pointer of that type. The following is an example of using the new keyword:

var p *int
p = new(int)

In this example, we use the new keyword to create a pointer p pointing to an integer type. We can use pointer p to access the newly allocated memory space of integer type.

However, if we try to pass a structure type to new as a parameter, for example:

type Person struct {
    name string
    age int
}

var p *Person
p = new(Person)

This is divided into two steps. First, a structure type named Person is defined. Then use the new keyword to allocate memory space for it. Similarly, we can use pointer p to access the newly allocated memory space of type Person.

So, what type of parameters should we pass to the new keyword? In fact, the new keyword in Golang can accept any type of parameters. Specifically, its type parameter can be a built-in type, a custom type, a structure type, an array type, or even an empty interface type. There are no restrictions between these types, and any type can be used as a parameter of new.

No matter which type it is, new will allocate enough memory space on the heap and return their corresponding pointers. Therefore, we can safely pass any type of variable or value to new, and it will allocate memory space for it and return a pointer of the corresponding type.

It should be noted that in Golang, pointer types support nil values, that is, pointers can be null. This means that if we use new to allocate memory and assign it to a pointer variable, the initial value of the pointer variable will be nil. For example:

var p *Person
p = new(Person)
fmt.Println(p) // 输出 nil

In this example, we define a pointer variable p pointing to the Person type and use the new keyword to allocate memory space for it. Since new returns a pointer type, and the default value of the pointer type is nil, the initial value of variable p is nil.

To summarize, the new keyword in Golang can be used to allocate memory for any type of variable or value and return a pointer of the corresponding type. Since pointer types support nil values, the initial value of pointer variables created using the new keyword is nil. When using new, we do not need to consider type restrictions, we only need to pass the corresponding variables or values ​​as needed.

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