Map types are reference types, like pointers or slices, and so the value of m above is nil; it doesn't point to an initialized map. A nil map behaves like an empty map when reading, but attempts to write to a nil map will cause a runtime panic; don't do that.

A map maps keys to values. The zero value of a map is nil. A nil map has no keys, nor can keys be added. The make function returns a map of the given type, initialized and ready for use.

Sep 21, 2023 · You can read from a nil map, but cannot write to it. The language spec says: A nil map is equivalent to an empty map except that no elements may be added.

Jul 24, 2023 · You can easily define that a nil-channel is never ready for communication, so reads block forever. You can safely define that a map/slice/channel that is nil has length (and capacity) 0. You can safely say that a range over a nil map/slice never iterates, as …

Sep 29, 2021 · nil has no cost. A map is a complex data structure and even an empty map uses nontrivial amount of memory. Creating a map does have a cost. If you have a map you never use (which could be frequent use case in e.g. json decoding), it's much cheaper to create it …

The Nile [b] (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa.

Jun 11, 2018 · A common beginner mistake in Go is forgetting to allocate the space for a map. Declaring variables with the map type will only default the map to nil. If you add an item to a nil map you...

In Go, nil can represent zero values of the following kinds of types: pointer types (including type-unsafe ones). map types. slice types. function types. channel types. interface types. Each of other predeclared identifiers in Go has a default type. For example, the default types of true and false are both bool type.

Jan 7, 2023 · I’ve been a bit confused for a while over when a map in Golang gets created with a value of nil (its zero value) and when it does not, so I’m writing this to help me remember. Let’s look at various ways to initialize a map: m1 := map[string]string{} // initializes map. m2 := make(map[string]string) // also initializes map.

Nov 6, 2018 · However, nil-slices and nil-maps can still be used and does not have to be initialized before we start using them. nil-maps. Maps will always return the zero-value of the value if it is nil, the same behaviour as if the key of the map is non-existent. The code. var p map[int]string // nil map fmt.Printf(" %#v length %d \n", p[99], len(p))