add validators to checkable classes

1 files changed, 8 insertions, 1 deletions

diff --git a/src/types.ts b/src/types.ts
index 39d374069..8f24fda90 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -360,8 +360,15 @@ interface Merchant {
   instance?: string;
 }
 
-@Checkable.Class
+@Checkable.ClassWithValidator
 export class Contract {
+
+  validate() {
+    if (this.exchanges.length == 0) {
+      throw Error("no exchanges in contract");
+    }
+  }
+
   @Checkable.String
   H_wire: string;