Blocks
In go a block is defined with a set of {}. Usually when we create a function we are in a block already. But we can define a block pretty much anywhere.
i := 10
{
i := 5
fmt.Println(i) // i is 5
}
fmt.Println(i) // i is 10
Scope
Scope defines where certain variable would be defined in. A scope can be block scoped, function scoped or package scoped. Each scope encompasses the previous. A package scoped variable would be available to the function and block but not the other way around.
x := 10
var z int // z declared here
{
fmt.Println(x) // this is fine
y := 15
z = 20 // defined here
}
fmt.Println(y) // this is not fine
fmt.Println(z) // this is fine
Shadowing
We can shadow any variable that is defined in the outer scope.
x := 10
{
x := 15
{
x := 20
fmt.Println(x) // 20
}
fmt.Println(x) // 15
}
fmt.Println(x) // 10
Just block level shadowing is uncommon. There are rare use cases for this. But I haven’t found really good use case for block level shadowing or even for blocks for that matter.
Next Steps
This is Part 6 of this Go crash course series.