开始，这是您分配和初始化所需了解的所有内容吗？

Question

It is just mind boggling how many different ways Go has for variable initialization. May be either i don't understand this completely or Go is a big after thought. Lot of things don't feel natural and looks like they added features as they found them missing. Initialization is one of them.

Here is running app on Go playground showing different ways of initialization

Here is what i understand

1. There are values and pointers. Values are initiated using var = or :=.
2. := only works inside the methods
3. To Create value and reference you use new or &. And they only work on composite types.
4. There are whole new ways of creating maps and slices
5. Create slice and maps using either make or var x []int. Noticing there is no = or :=

Are there any easy way to understand all this for newbies? Reading specs gives all this in bits and pieces everywhere.

Answer 1

Yeah, this was one of those things that I found confusing early as well. I've come up with my own rules of thumb which may or may not be best practices, but they've served me well. Tweaked after comment from Stephen about zero values

1. Use := as much as possible, let Go infer types

2. If you just need an empty slice or map (and don't need to set an initial capacity), use {} syntax

   s := []string{}
m := map[string]string{}

3. The only reason to use var is to initialize something to a zero value (pointed out by Stephen in comments) (and yeah, outside of functions you'll need var or const as well):

   var ptr *MyStruct // this initializes a nil pointer
var t time.Time // this initializes a zero-valued time.Time