How to access children

Page Content hide
1 Children
2 Grandchildren
3 Arrays
4 How many children
5 Testing if a child exists
6 Storing objects as values
7 Navigation
8 Access shortcuts
9 cJobject deep dive

Children

As mentioned in the introduction, each cJobject is either a key/value pair or is the parent of some more cJobjects. Accessing the children of a cJobject is straightforward, and as close to the JavaScript as possible within the confines and rules of the VBA language syntax.


By key , for example 

job.child("somekey")


or by childIndex

job.children(1)

This is roughly equivalent to job.somekey or job[0] in JavaScript except that cjobject has a childIndex for both array members and regular objects (JavaScript only has indices for Arrays), and the cJobject index starts at 1 (JavaScript starts at 0)

Grandchildren

You can access grandchildren and so on in a couple of ways too

job.child("achild").child("agrandchild").child("agreatgrandchild")

is equivalent to

job.child("achild.agrandchild.agreatgrandchild")

which is close to the JavaScript

job.achild.agrandchild.agreatgrandchild

You can also mix index and named keys, so 

job.children(1).child("name")

is equivalent to

job.child("1.name")

  and the JavaScript equivalent 

job[0].name

Arrays

As mentioned arrays are not really much different to regular objects, except that their key is the same value as their childIndex. 


Using the test data from cJobject deep dive here’s an example of extracting and stringifying the the first array member 

Set child = job.children(1)    
Debug.Print child.stringify

{"name":"john","age":25}

We can print the value of the name property of the first array member

Debug.Print job.children(1).child("name").value

john

Which is equivalent to this

Debug.Print job.child("1.name").value

john

Note that we can always stringify (convert to JSON) any cJobject – even a single property

Debug.Print job.child("1.name").stringify

{"name":"john"}

How many children

You can test if a cJobect has children like this

if (job.hasChildren) then ...

The number of children is

job.children.count

job.hasChildren is equivalent to job.children.count > 0. In JavaScript you could only do this test ( if (job.length > 0) )  on an Array. For an object you would need to say …  if (Object.keys(job).length > 0)

Testing if a child exists

Accessing a child that doesn’t exist will return Nothing, so you can simply test any of the syntax already mentioned for Nothing.

if (not job.child("2.age") is nothing) then ...

for convenience, I provide an isSomething()  function also, so the above is equivalent to

if (isSomething (job.child("2.age") ) ) then ...

This is roughly equivalent to the JavaScript 

if(typeof job[1].age === typeof undefined) { ...

except that JavaScript will throw an error if job is not an Array,  or element 1 does not exist, only making a successful test on the final property – age. cJobject will not fail, but return Nothing.

Now let’s look at some more cJobject topics.

For more on this see How to use cJobject