Golang : When to use make or new?

Problem :

When to use make or new in Golang ? It can be confusing for newbie to Golang.

Solution :

In the simplest example that I can think of....

• Imagine new as someone that creates an empty box and points the direction(pointer or address) of the empty box to you.
• and make as someone that creates a box filled with values that defined by you and pass the non-empty box to you....not pointer or address.

Use new when you want to :

• create a new file and save data to the the NEW file
• create or allocate a new buffer for you to store some data, manipulate the buffer and then flush the data to somewhere else such as a pipe.

Use make when you want to :

• use maps, slices and channels and want to manipulate the data in them directly instead of a pointer or address.
• pre-fill the maps, slices and channels with initial values.
• specify the size or increase/decrease the size of maps or slices during runtime.

Remember...the rule of the thumb is

• new = empty box with pointer
• make = filled box without pointer

Hope this simple tutorial can be useful to you. Happy coding!

Reference :

http://golang.org/doc/effectivego.html#allocationnew