[]T是包含指針的切片，適用於共享結(jié)構(gòu)體或避免複製大數(shù)據(jù)；[ ]T是指向切片的指針，用於修改切片本身。 1. []T每個元素都是指針，適合處理大型結(jié)構(gòu)、共享對像或可選元素；2. [ ]T用於函數(shù)內(nèi)修改切片頭、多函數(shù)共享切片或性能敏感場景；3. 兩者用途不同，混用會導(dǎo)致行為混亂，例如函數(shù)內(nèi)追加需用*[ ]T才能修改原切片。

Go handles []*T (a slice of pointers) and *[]T (a pointer to a slice) quite differently, even though both involve slices and pointers. The difference lies in what's being pointed to and how data is shared or modified.

What []*T Really Means

This is a slice where each element is a pointer to a value of type T . It's commonly used when you want each item in the slice to refer to some object elsewhere in memory — for example, if you're building a list of structs and don't want to copy them around.

A typical use case looks like this:

 type User struct {
    Name string
}

users := []*User{
    {Name: "Alice"},
    {Name: "Bob"},
}

Here, users is a slice of pointers to User . Each element is a pointer, so modifying one of them affects the same object across all references.

You might choose []*T when:

• You're working with large structs and want to avoid copying.
• You need changes to elements reflected elsewhere.
• You're managing objects that should be shared or mutable across functions.

One thing to watch out for: if you do something like this:

 u := User{Name: "Charlie"}
users = append(users, &u)

…you're storing the address of u , not a copy. If u changes later, every place it was referenced will see that change.

What *[]T Is For

This is a pointer to an entire slice. Since slices are already reference types in Go (internally they contain a pointer to an array), using a pointer to a slice is less common — but still useful in certain situations.

For example, if you want a function to modify the slice itself (like changing its length or capacity), you might pass a pointer to it:

 func addNames(s *[]string) {
    *s = append(*s, "NewName")
}

Then call it like:

 names := []string{"Alice"}
addNames(&names)

So *[]T comes in handy when:

• You need to modify the slice header (eg, reallocate, reset).
• You're passing the slice into multiple functions and want all to affect the same underlying slice header.
• You're trying to avoid copying the slice header in performance-sensitive code (though this is rare).

But keep in mind: just because you have a pointer to a slice doesn't mean the underlying data gets smaller or faster. The slice header is small, so in most cases, passing []T directly is perfectly fine.

When to Use Which?

Use []*T when:

• Elements are large structs.
• You want to share access to the same instance.
• You're building a collection where individual items may be nil or optional.

Use *[]T when:

• You need to modify the slice header inside a function.
• You're dealing with a receiver in a method set and want to allow mutation.

It's also possible to combine them — for example, *[]*T would be a pointer to a slice of pointers, which is occasionally seen in more complex data structures.

One Common Gotcha

When appending to a slice passed by value ( []T ), the original slice outside the function won't change. That's why sometimes people reach for *[]T — not because the slice data needs to be shared, but simply to update where the slice points or its length/capacity.

If you write:

 func badAppend(s []string) {
    s = append(s, "new")
}

And then call:

 s := []string{"a"}
badAppend(s)

s will still only have "a" in it. Because the function got a copy of the slice header, not a reference to it.

To fix that without returning a new slice, you'd use *[]T .

So, in short:

• []*T is about having a collection of references.
• *[]T is about being able to modify the slice header itself.

They serve different purposes, and mixing them up can lead to confusing behavior — especially when passing slices into functions expecting one or the other.

基本上就這些。

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