2D slice, array. In the Go language we model 2D things with slices of slices. In the 2 levels of nesting we store the 2 dimensions.
Appending data. To create a 2D slice, we use append() to add each row. Then we can access the data by indexing through the slices.
Slice example. Consider a slice of slices: we could use the term "jagged" to describe nested slices. Each sub-slice can be any number of elements long.
Step 1 Initially we create an empty slice of slices—it has no top-level slice elements.
Step 2 Here we create 2 rows (which are also slices). And with append() we add the two rows to the "values."
Step 3 We can access entire rows with the first index. Row 0 is the first row, and row 1 is the second row.
Step 4 With 2 indexes, we address a single int element. We can get or set an integer in the nested slices.
package main
import "fmt"
func main() {
// Step 1: create empty collection.
values := [][]int{}
// Step 2: these are the first two rows.// ... Append each row to the two-dimensional slice.
row1 := []int{1, 2, 3}
row2 := []int{4, 5, 6}
values = append(values, row1)
values = append(values, row2)
// Step 3: display first row, and second row.
fmt.Println("Row 1")
fmt.Println(values[0])
fmt.Println("Row 2")
fmt.Println(values[1])
// Step 4: access an element.
fmt.Println("First element")
fmt.Println(values[0][0])
}Row 1
[1 2 3]
Row 2
[4 5 6]
First element
1
2D arrays. To create a 2D array we must specify each dimension. We can then assign individual elements within the array. Here we create a 2 by 2 array of strings.
Tip Arrays in Go have fixed sizes. We must specify the size of the array. For variable-size collections, slices are better.
package main
import "fmt"
func main() {
// Create two-dimensional array.
letters := [2][2]string{}
// Assign all elements in 2 by 2 array.
letters[0][0] = "a"
letters[0][1] = "b"
letters[1][0] = "c"
letters[1][1] = "d"// Display result.
fmt.Println(letters)
}[[a b] [c d]]
Nested string slices. Here we use strings in nested slices. Each slice does not have the same length: this is a jagged slice. We loop over the nested slices with for.
Detail The range built-in returns all indexes (in order) of the animals slice. We then access each nested slice of animal names.
package main
import "fmt"
func main() {
// Create an empty slice of slices.
animals := [][]string{}
// Create three string slices.
row1 := []string{"fish", "shark", "eel"}
row2 := []string{"bird"}
row3 := []string{"lizard", "salamander"}
// Append string slices to outer slice.
animals = append(animals, row1)
animals = append(animals, row2)
animals = append(animals, row3)
// Loop over slices in animals.
for i := range animals {
fmt.Printf("Row: %v\n", i)
fmt.Println(animals[i])
}
}Row: 0
[fish shark eel]
Row: 1
[bird]
Row: 2
[lizard salamander]
Some data sources are often stored in a two-dimensional plane. This can be efficient. But often, using a map is a good option—it saves space in sparse collections.
A review. Idiomatic Go is code that matches the language's popular usage. In Go we usually prefer slices (not arrays). So a 2D slice is an ideal solution.
Dot Net Perls is a collection of pages with code examples, which are updated to stay current. Programming is an art, and it can be learned from examples.
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This page was last updated on Apr 21, 2023 (edit).