add ability to provide global default mapping; add docs for same

README.md

@@ -4,6 +4,8 @@ Truffle Object Mapper
 
 Quickly and painless dump all the values from a deployed contract.
 
+See [Object Mapper](https://github.com/wankdanker/node-object-mapper#readme) for full details on output mapping syntax.
+
 ## Quick Usage
 
 ```JavaScript
@@ -18,7 +20,7 @@ const mapper = new Mapper();
 })();
 ```
 
-## Customize Output for Types
+### Customize Output for Types
 
 ```JavaScript
 const mapper = new Mapper({
@@ -32,11 +34,41 @@ const mapper = new Mapper({
 const values = await mapper.map('Token', '0xf793db07d9952ff75d5371cceb98c4380277503f');
 ```
 
-## Change Output Mapping
+### Provide Custom Output Mapping
 
 See [Object Mapper](https://github.com/wankdanker/node-object-mapper#readme) for full details on output mapping.
 
 ```JavaScript
+
+// all calls to .map will apply these transformations
+const mapper = new Mapper({
+  mapping: {
+    // example: 'State' is an integer representing a struct
+    // this will output two keys:
+    //  'state' - the integer
+    //  'stateName' - the string representing the struct
+    State: [
+      {
+        key: 'state',
+        transform: function (val) {
+          const index = Number(val.toString());
+          const states = ['Funding', 'Active', 'Matured'];
+          return states[index];
+        },
+      },
+      'stateName',
+    ],
+  },
+});
+
+
+```
+
+### Change Output Mapping Each Time
+
+```JavaScript
+
+// this custom mapping only applies to this call of .map
 const values = await mapper.map('Token', '0xf793db07d9952ff75d5371cceb98c4380277503f', {
   // map the property 'name' to the output key 'tokenName'
   name: 'tokenName',
@@ -62,3 +94,6 @@ const values = await mapper.map('Token', '0xf793db07d9952ff75d5371cceb98c4380277
   }],
 });
 ```
+
+## API Methods
+

example.js

@@ -0,0 +1,38 @@
+'use strict';
+
+const Mapper = require('./');
+const Web3 = require('web3');
+
+function bNToString(val) {
+  return Web3.utils.BN(val).toString();
+}
+
+const mapper = new Mapper({
+  mapping: {
+    State: [
+      {
+        key: 'state',
+        transform: function (val) {
+          const index = Number(val.toString());
+          const states = ['Funding', 'Active', 'Matured'];
+          return states[index];
+        },
+      },
+      'stateName',
+    ],
+  },
+  types: {
+    int8: bNToString,
+    uint256: bNToString,
+  },
+  workingDirectory: __dirname,
+});
+
+(async () => {
+  try {
+    const values = await mapper.map('Token', '0x468d834b0FAc4B9D8B2E90bE1cE35A891Ff96Ae9');
+    console.log(values);
+  } catch (err) {
+    console.error(err);
+  }
+})();

lib/object-mapper.js

@@ -24,6 +24,7 @@ class TruffleObjectMapper {
     this.options = merge(defaults, options);
     this.artifacts = {};
     this._types = merge(TruffleObjectMapper.types, options.types || {});
+    this._mapping = this.options.mapping || {};
   }
 
   getArtifact(contractName) {
@@ -88,11 +89,12 @@ class TruffleObjectMapper {
       const value = await instance[node.name]();
       values[key] = value;
       const [output] = node.outputs;
-      map[key] = this.buildOutputMapping(key, output.type, mapping[key]);
+      const customMapping = this._mapping[key] ?
+        this._mapping[key] :
+        mapping[key];
+      map[key] = this.buildOutputMapping(key, output.type, customMapping);
     });
 
-    console.log(map);
-
     return objectMapper(values, map);
   }