#5.1 Why can't I use Blockchain for data? #2
Description
main.go
package main
import (
"html/template"
"log"
"net/http"
Blockchain "github.com/achievermina/gocoin/blockchain"
)
const port string = ":8000"
type data struct {
Blocks *Blockchain // I tried to use Blockchain instead of block[]. I have an error here. Can you let me know why? @serranoarevalo
}
func home(rw http.ResponseWriter, r *http.Request) {
tmpl := template.Must(template.ParseFiles("templates/home.gohtml"))
data := data{Blockchain.GetBlockchain()}
tmpl.Execute(rw, data)
}
func main() {
chain := Blockchain.GetBlockchain()
chain.AddBlock("Second")
chain.AddBlock("Third Block")
http.HandleFunc("/", home)
log.Fatal(http.ListenAndServe(port, nil))
}
blockchain.go
package blockchain
import (
"crypto/sha256"
"fmt"
"sync"
)
type Block struct {
Data string
Hash string
PrevHash string
}
type Blockchain struct {
Blocks []*Block
}
var b *Blockchain
var once sync.Once
func createBlock(data string) *Block {
newBlock := Block{data, "", b.getLastHash()}
newBlock.createHash()
return &newBlock
}
func GetBlockchain() *Blockchain {
if b == nil {
once.Do(func () {
b = &Blockchain{}
b.Blocks = append(b.Blocks, createBlock("First Block"))
})
}
return b;
}
func (b* Block) createHash() {
hash := sha256.Sum256([]byte(b.Data + b.PrevHash))
b.Hash = fmt.Sprintf("%x", hash)
}
func (b* Blockchain) getLastHash() string {
if (len(b.Blocks) > 0 ) {
return b.Blocks[len(b.Blocks)-1].Hash
}
return ""
}
func (b* Blockchain) AddBlock(data string) {
b.Blocks = append(b.Blocks, createBlock(data))
}
func(b* Blockchain) PrintBlocks() {
for _, Block := range b.Blocks {
fmt.Printf("Data: %s \n", Block.Data)
fmt.Printf("Hash: %s \n", Block.Hash)
fmt.Printf("PrevHash: %s \n", Block.PrevHash)
}
}