CODEWITHSUNDEEP
meteor
Scott
Scott

Reputation: 385

Cannot read property of undefined, but property exists

I am getting a curious error in a template helper and I was hoping someone could lay eyes on it with me. Basically the error I'm getting in the console of the client is that the getArena().height is undefined. However, console.log(getArena().height) returns the correct property value. It appears to be a timing issue causing me to get the error, but my application is actually working. What can I do to alleviate this console error?

    //My template helper function
yGrids: function() {

        console.log(getArena);
        console.log(getArena().height);
        var yArray = [];
        for (var i=0;i<(getArena().height);i++){
            yArray.push({});
        }
        return yArray;
    },


// The console results
function getArena() {                                                                                              // 50
    return Arenas.findOne(Session.get('arena_id'));                            …
Exception in template helper: TypeError: Cannot read property 'height' of undefined
    at Object.yGrids (http://localhost:3000/app/app.js?hash=c17abf51d6af6541e868fa3fd0b26e34eea2df28:94:35)
    at http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:2994:16
    at http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:1653:16
    at http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:3046:66
    at Function.Template._withTemplateInstanceFunc (http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:3687:12)
    at http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:3045:27
    at Object.Spacebars.call (http://localhost:3000/packages/spacebars.js?hash=65db8b6a8e3fca189b416de702967b1cb83d57d5:172:18)
    at http://localhost:3000/app/app.js?hash=c17abf51d6af6541e868fa3fd0b26e34eea2df28:24:22
    at .<anonymous> (http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:2754:17)
    at http://localhost:3000/packages/blaze.js?hash=ef41aed769a8945fc99ac4954e8c9ec157a88cea:1875:20
function getArena() {                                                                                              // 50
    return Arenas.findOne(Session.get('arena_id'));                            …
2

Upvotes: 0

Views: 548

Answers (2)

khem poudel
khem poudel

Reputation: 587

Whatever getArena() returns you ought to store it in the reactive variable by setting the reactive variable and you can access the reactive var in helper by get() method

Upvotes: 0

Michel Floyd
Michel Floyd

Reputation: 20226

This is a very common issue in Meteor helpers when referring to a collection which may not yet have been loaded via a subscription. In general you want to show a loading template instead of your actual layout until your subscription is ready. Or (less elegant) you can defend yourself with:

var arena = getArena();
var height = arena && arena.height;

Upvotes: 1

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