CODEWITHSUNDEEP
node.jsexpresspug
rokirakan78
rokirakan78

Reputation: 251

Issue with MySQL + Node.js + Jade on select data

Error

Problem: Cannot read property 'length' of undefined at jade_debug.unshift.lineno (eval at (C:\Users\Dev\Node_js\node_modules\jade\lib\jade.js:160:8), :111:31) at eval (eval at (C:\Users\Dev\Node_js\node_modules\jade\lib\jade.js:160:8),

DB function

exports.selectRows = function(){
    var objBD = BD();
    objBD.query('SELECT * FROM usr ', function(results) {
        return(results);

    });
}

Route

exports.index = function(req, res) {
    res.render('customer/index',{ customers: db.selectRows() });
};

index.jade

each item in customers
  tr
    td
      a(href='/customer/details/#{item.id}') #{item.id}
    td #{item.name}
    td #{item.email}
    td #{item.phone}

Upvotes: 1

Views: 1447

Answers (1)

Tom
Tom

Reputation: 26849

Problem with your code is that the selectRows method is executed asynchronously and db.selectRows() expression in your handler method always return undefined value and hence the execption (customers template variable is undefined).

You should add the following changes to your code in order to have it working correctly:

DB function : 

exports.selectRows = function(callback){
    var objBD = BD();
    objBD.query('SELECT * FROM usr ', callback);
}

Route: 

exports.index = function(req, res) {
    db.selectRows(function(results){
        res.render('customer/index', { customers: results });
    });
}

Sometimes you may have a situation (very common Node.js pattern) where your callback gets two parameters:

  • first would be an error - it should be undefined if DB query was successful
  • second would be DB query results data

In case of two parameters (error and results) your route should look as follows: 

exports.index = function(req, res) {
    db.selectRows(function(err, results){
        if (err) return res.send(500, "DB QUERY ERROR");
        res.render('customer/index', { customers: results });
    });
}

You can also simplify your index.jade

each item in customers
  tr
    td: a(href='/customer/details/#{item.id}')= item.id
    td= item.name
    td= item.email
    td= item.phone

I hope that will help.

Upvotes: 1

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