examples: add _deploy usage examples

Close #1466

examples/runtime/runtime.go

@@ -16,6 +16,14 @@ func init() {
 	trigger = runtime.GetTrigger()
 }
 
+func _deploy(isUpdate bool) {
+	if isUpdate {
+		Log("_deploy method called before contract update")
+		return
+	}
+	Log("_deploy method called before contract creation")
+}
+
 // CheckWitness checks owner's witness
 func CheckWitness() bool {
 	// Log owner upon Verification trigger

examples/timer/timer.go

@@ -0,0 +1,96 @@
+package timer
+
+import (
+	"github.com/nspcc-dev/neo-go/pkg/interop/contract"
+	"github.com/nspcc-dev/neo-go/pkg/interop/engine"
+	"github.com/nspcc-dev/neo-go/pkg/interop/runtime"
+	"github.com/nspcc-dev/neo-go/pkg/interop/storage"
+	"github.com/nspcc-dev/neo-go/pkg/interop/util"
+)
+
+const defaultTicks = 3
+
+var (
+	// ctx holds storage context for contract methods
+	ctx storage.Context
+	// Check if the invoker of the contract is the specified owner
+	owner = util.FromAddress("NULwe3UAHckN2fzNdcVg31tDiaYtMDwANt")
+	// ticksKey is a storage key for ticks counter
+	ticksKey = []byte("ticks")
+)
+
+func init() {
+	ctx = storage.GetContext()
+}
+
+func _deploy(isUpdate bool) {
+	if isUpdate {
+		ticksLeft := storage.Get(ctx, ticksKey).(int) + 1
+		storage.Put(ctx, ticksKey, ticksLeft)
+		runtime.Log("One more tick is added.")
+		return
+	}
+	storage.Put(ctx, ticksKey, defaultTicks)
+	runtime.Log("Timer set to " + itoa(defaultTicks) + " ticks.")
+}
+
+// Migrate migrates the contract.
+func Migrate(script []byte, manifest []byte) bool {
+	if !runtime.CheckWitness(owner) {
+		runtime.Log("Only owner is allowed to update the contract.")
+		return false
+	}
+	contract.Update(script, manifest)
+	runtime.Log("Contract updated.")
+	return true
+}
+
+// Tick decrement ticks count and checks whether the timer is fired.
+func Tick() bool {
+	runtime.Log("Tick-tock.")
+	ticksLeft := storage.Get(ctx, ticksKey)
+	ticksLeft = ticksLeft.(int) - 1
+	if ticksLeft == 0 {
+		runtime.Log("Fired!")
+		return engine.AppCall(runtime.GetExecutingScriptHash(), "selfDestroy").(bool)
+	}
+	storage.Put(ctx, ticksKey, ticksLeft)
+	runtime.Log(itoa(ticksLeft.(int)) + " ticks left.")
+	return true
+}
+
+// SelfDestroy destroys the contract.
+func SelfDestroy() bool {
+	if !(runtime.CheckWitness(owner) || runtime.CheckWitness(runtime.GetExecutingScriptHash())) {
+		runtime.Log("Only owner or the contract itself are allowed to destroy the contract.")
+		return false
+	}
+	contract.Destroy()
+	runtime.Log("Destroyed.")
+	return true
+}
+
+// itoa converts int to string
+func itoa(i int) string {
+	digits := "0123456789"
+	var (
+		res        string
+		isNegative bool
+	)
+	if i < 0 {
+		i = -i
+		isNegative = true
+	}
+	for {
+		r := i % 10
+		res = digits[r:r+1] + res
+		i = i / 10
+		if i == 0 {
+			break
+		}
+	}
+	if isNegative {
+		res = "-" + res
+	}
+	return res
+}

examples/timer/timer.yml

@@ -0,0 +1,4 @@
+hasstorage: true
+ispayable: false
+supportedstandards: []
+events: []