extjs: How to l set value for combobox when loading

Question

1. I am looking for a load listener, that when the combobox is up, load will be called and preform an ajax to the s

Answer 1

As a general solution to the problem, I've gone with

listeners:{
    scope: this,
    afterRender: this.selectFirstComboItem
}

with

selectFirstComboItem: function(combo) {
    // This will tell us if the combo box has loaded at least once
    if (typeof combo.getStore().lastOptions !== "undefined") {
        // Grab the first value from the store
        combo.setValue(combo.getStore().first().get(combo.valueField));
    }
    else {
        // When the store loads
        combo.getStore().on("load", function(store, items){
            // Grab the first item of the newly loaded data
            combo.setValue(items[0].get(combo.valueField));
        });
    }
}