I am currently stuck on an issue I am having getting the value of the ui:inputCheckbox Lightning component. In the Lightning Component Developer Guide, the following example is provided:

COMPONENT MARKUP

<aura:component>
    <aura:attribute name="myBool" type="Boolean" default="true"/>
    <ui:inputCheckbox aura:id="checkbox" label="Select?" change="{!c.onCheck}"/>
    <p>Selected:</p>
    <p><ui:outputText class="result" aura:id="checkResult" value="false"/></p>
    <p>The following checkbox uses a component attribute to bind its value.</p>
    <ui:outputCheckbox aura:id="output" value="{!v.myBool}"/>
</aura:component>

COMPONENT CONTROLLER
 

({
        onCheck: function (cmp, event, helper) {
            var checkCmp = cmp.find("checkbox");
            resultCmp = cmp.find("checkResult");
            resultCmp.set("v.value", "" + **checkCmp.get("v.value")**);
        }
    })

I am currently using the exact pattern in my markup as follows:

MY COMPONENT MARKUP

<div class="pbxs">
         <div class="tc wht pas mhauto"></div>
         <ui:inputCheckbox aura:id="taskCheckBox" text="{!nextsteps.task.Id}"  class="sq-25 checkbox checkbox--default checkbox--states-1 brm mrs bg-secondary-btn sq-22 a-mid dib" change="{!c.handleCheckTask}"/>                                        
    </div>

MY COMPONENT CONTROLLER

handleCheckTask : function(cmp, event, helper) {
            var checkCmp = cmp.find("taskCheckBox");
            console.log("value : " + **checkCmp.get("v.value")**)
    }

Strangely, when I click the checkbox in my component, I get the following aura error:

"Uncaught error in markup://ui:change : checkCmp.get is not a function"

I am not sure why I am getting that error when I am using the same pattern as in the example. I tried re-creating the example from the guide. When I did that, I did not get the error. Can anyone see what I might be missing?