Catch-all getters and setters in ECMAScript 4

While reading the Tamarin and ECMAScript 4 presentation by John Resig I learned about the Catch-all getters and setters feature of ECMAScript 4.

This feature allows you to handle the request for a non declared property of an object. It is similar to Python's __getattr__/__setattr__.

An example of the syntax is the following:

dynamic class MyDynamicClass {
   meta function get(name) {
      return name+" requested.";
   }
   meta function set(name,value) {
      print("setting:"+name+" to "+value);
   }
} 

A use of this class:

>> let w = new MyDynamicClass()
>> w.foo
foo requested.
>> w.goo = 4
setting:goo to 4
4

I wanted to write a example created for previous posts using the ECMAScript 4 reference implementation. This example consists of two classes CsvFile and CsvFileEntry the first represents a complete csv file and the second is just one entry. The catch-all mechanism will be used to access the fields of the entry.

The implementation for the CsvFileEntry class is the following:

dynamic class CsvFileEntry {
    let headers : Map.<string,int>;
    let data : *;
    public function CsvFileEntry(data,headers : Map.<string,int>) {
       this.data = data;
       this.headers = headers;
    }
    meta function get(name) {
       let columnIndex = headers.get(name);
       if (columnIndex != null) {
           return data[columnIndex];
       } else {
           return null;
       }
    }
}

The CsvFile implementation is the following:

use namespace intrinsic;
class CsvFile {
   let headers : Map.<string,int>;
   let content : Array;
   public function CsvFile(filename:string) {
      let fileContent = intrinsic::readFile(filename);
      let rows = fileContent.split('\n');
      headers = new Map.<string,int>();
      content = new Array();
      let i = 0;
      for (let rowIndex = 0; rowIndex < rows.length;rowIndex++) {
         let row = rows[rowIndex];
         let data = row.split(',');
         if (i == 0) {
            for(let j = 0;j < data.length;j++) {
                headers.put(data[j],j);
            }
         } else {
            content.push(new CsvFileEntry(data,headers));
         }
         i++;
      }
   }
   public function get Content() {
      return content;
   }
}

Given that we have the following file (cars.csv):

Year,Make,Model
1997,Ford,E350
2000,Mercury,Cougar

...we can use of the CsvFile class:

>> let f = new CsvFile('cars.csv')
>> f.Content[0].Model
E350
>> f.Content[0].Year
1997