diff --git a/__crypto/simple_contract/src/credit.rs b/__crypto/simple_contract/src/credit.rs
index d448128..011acf8 100644
--- a/__crypto/simple_contract/src/credit.rs
+++ b/__crypto/simple_contract/src/credit.rs
@@ -5,6 +5,7 @@ use crate::{tx::Transaction};
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct CreditContract {
+    pub name: String,
     pub credit_limit: u32,
     pub issue_amount: u32,
     pub admin: String,
@@ -14,15 +15,19 @@ pub struct CreditContract {
 impl CreditContract {
     pub fn new(tx: &Transaction, name: &str, credit_limit: u32) -> XResult<Self> {
         let c = Self {
+            name: name.into(),
             credit_limit,
             issue_amount: 0,
             admin: tx.sender.clone().unwrap(),
             credit: HashMap::new(),
         };
-        Self::save(name, &c)?;
         Ok(c)
     }
 
+    pub fn load(name: &str) -> XResult<Self> {
+        load_credit_contract(name)
+    }
+
     pub fn issue(&mut self, tx: &Transaction, receiver: &str, credit: u32) -> XResult<()> {
         if &self.admin != tx.sender.as_ref().ok_or_else(|| SimpleError::new("Sender is not provided".into()))? {
             return simple_error!("Current user is not admin, {} vs {:?}", self.admin, tx.sender);
@@ -35,6 +40,7 @@ impl CreditContract {
             Some(cr) => *cr += credit,
         }
         self.issue_amount += credit;
+        save_credit_contract(self)?;
         Ok(())
     }
 
@@ -53,26 +59,32 @@ impl CreditContract {
                 }
             },
         }
+        save_credit_contract(self)?;
         Ok(())
     }
 
-    pub fn get(&self, _tx: &Transaction, account: &str) -> u32 {
+    pub fn query(&self, _tx: &Transaction, account: &str) -> u32 {
         match self.credit.get(account) {
             None => 0,
             Some(receiver_credit) => *receiver_credit,
         }
     }
 
-    pub fn load(name: &str) -> XResult<Self> {
-        let json = fs::read_to_string(name)?;
-        serde_json::from_str(&json).map_err(|e| e.into())
-    }
-
-    pub fn save(name: &str, c: &CreditContract) -> XResult<()> {
-        if let Ok(_) = File::open(name) {
-            return simple_error!("File exists: {}", name);
-        }
-        fs::write(name, serde_json::to_string(c)?.as_bytes())?;
-        Ok(())
+    pub fn query_all(&self, _tx: &Transaction) -> &HashMap<String, u32> {
+        &self.credit
     }
 }
+
+fn load_credit_contract(name: &str) -> XResult<CreditContract> {
+    let json = fs::read_to_string(name)?;
+    serde_json::from_str(&json).map_err(|e| e.into())
+}
+
+fn save_credit_contract(c: &CreditContract) -> XResult<()> {
+    let name = &c.name;
+    if let Ok(_) = File::open(name) {
+        return simple_error!("File exists: {}", name);
+    }
+    fs::write(name, serde_json::to_string(c)?.as_bytes())?;
+    Ok(())
+}