examples: update examples

Closes #1234

examples/storage/storage.go

@@ -5,78 +5,39 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/interop/storage"
 )
 
-// Main is a very useful function.
-func Main(operation string, args []interface{}) interface{} {
-	if operation == "put" {
-		return Put(args)
-	}
+// ctx holds storage context for contract methods
+var ctx storage.Context
 
-	if operation == "get" {
-		return Get(args)
-	}
-
-	if operation == "delete" {
-		return Delete(args)
-	}
-
-	if operation == "find" {
-		return Find(args)
-	}
-
-	return false
+// init inits storage context before any other contract method is called
+func init() {
+	ctx = storage.GetContext()
 }
 
 // Put puts value at key.
-func Put(args []interface{}) interface{} {
-	ctx := storage.GetContext()
-	if checkArgs(args, 2) {
-		key := args[0].([]byte)
-		value := args[1].([]byte)
-		storage.Put(ctx, key, value)
-		return key
-	}
-	return false
+func Put(key, value []byte) []byte {
+	storage.Put(ctx, key, value)
+	return key
 }
 
 // Get returns the value at passed key.
-func Get(args []interface{}) interface{} {
-	ctx := storage.GetContext()
-	if checkArgs(args, 1) {
-		key := args[0].([]byte)
-		return storage.Get(ctx, key)
-	}
-	return false
+func Get(key []byte) interface{} {
+	return storage.Get(ctx, key)
 }
 
 // Delete deletes the value at passed key.
-func Delete(args []interface{}) interface{} {
-	ctx := storage.GetContext()
-	key := args[0].([]byte)
+func Delete(key []byte) bool {
 	storage.Delete(ctx, key)
 	return true
 }
 
-// Find returns an array of key-value pairs with key that matched the passed value.
-func Find(args []interface{}) interface{} {
-	ctx := storage.GetContext()
-	if checkArgs(args, 1) {
-		value := args[0].([]byte)
-		iter := storage.Find(ctx, value)
-		result := []string{}
-		for iterator.Next(iter) {
-			val := iterator.Value(iter)
-			key := iterator.Key(iter)
-			result = append(result, key.(string)+":"+val.(string))
-		}
-		return result
+// Find returns an array of key-value pairs with key that matched the passed value
+func Find(value []byte) []string {
+	iter := storage.Find(ctx, value)
+	result := []string{}
+	for iterator.Next(iter) {
+		val := iterator.Value(iter)
+		key := iterator.Key(iter)
+		result = append(result, key.(string)+":"+val.(string))
 	}
-	return false
-}
-
-func checkArgs(args []interface{}, length int) bool {
-	if len(args) == length {
-		return true
-	}
-
-	return false
+	return result
 }