Answers.Body: <p>There's no property called <code>xPosition</code>, and <code>transform</code> is a property of a layer, not a method, but you're on the right track. The expression has to return an array of two values [x, y], and the components of the position are stored in an array like that too. The expression you want — if you're applying it to the layer position property — is this:</p>
  
  <pre class="lang-js prettyprint-override"><code>xpos=thisComp.layer("Blue").effect("CC Particle World")("Position X");
  ypos=transform.position[1];
  [xpos, ypos]
  </code></pre>
  
  <p>That will apply the value of the <code>Position X</code> property of the effect to the <strong>X</strong> position of the layer, and the current <strong>Y</strong> value of the layer to the <strong>Y</strong>.</p>
  
  <p>If you're trying to use the layer's <strong>X</strong> position on the effect's Position <strong>X</strong> property then you need to use:</p>
  
  <pre class="lang-js prettyprint-override"><code>thisComp.layer("Blue").transform.position[0]
  </code></pre>
  
  <p>you only need one value for this property.</p>
  
  <blockquote>
    <p><strong>Pro Tip</strong> a great way to learn how properties are accessed in expressions, as well as being a super quick and typo-free way of
    creating them is to use the pickwhip. Next to the expression box
    you'll see a curly icon. Click that and drag it to the property you
    want to reference in your expression. So in the second case you could
    drag it to the number for the <strong>X</strong> value of the layer's position and it
    would give you the correct syntax for accessing it.  </p>
    
    <p><img src="https://i.sstatic.net/Z19IM.png" alt="enter image description here"></p>
  </blockquote>
  
  <p>A good place to learn more about expressions is Dan Ebbert's page: <a href="http://motionscript.com/" rel="nofollow noreferrer">http://motionscript.com/</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-05-26T14:08:08.010Z
Answers.Text: You're welcome, here is the meta: http://meta.video.stackexchange.com/questions/1449/syntax-highlighting, I hope we get a detailed explanation soon.
Answers.UserDisplayName: p2or
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-05-26T13:41:26.603Z
Answers.LastActivityDate: 2015-05-28T03:48:23.220Z
Answers.LastEditDate: 2015-05-28T03:48:23.220Z
Answers.UserDisplayName: stib
Body: <p>I have a layer called Blue.</p>
  
  <p>I applied CC Particular World to a ShapeLayer with an animated separated X Position (with 3 keyframes).</p>
  
  <p>The thing is that the effect doesn't move along with the shape.
  So either I animate the Producer features "Position X" with keyframes or I would parent this feature to xPosition.</p>
  
  <p>I just don't know if this is possible and if so how?</p>
  
  <p>I invented this script...</p>
  
  <pre><code>    thisComp.layer("Blue").effect("CC Particle World")("Position X").transform("xPosition")
  </code></pre>
  
  <p>it results in error!</p>
  
  <p>Thank you for your help.</p>
  
  <p>H.</p>
  
Tags: <after-effects-expressions>
Title: Parent a Position X from Particular World to it's own transform xPosition
UserDisplayName: Horacsio
ThreadText: # Parent a Position X from Particular World to it's own transform xPosition
  
  (Asked by: username_0 on 2015-05-25)
  
  I have a layer called Blue.
  
  I applied CC Particular World to a ShapeLayer with an animated separated X Position (with 3 keyframes).
  
  The thing is that the effect doesn't move along with the shape.
  So either I animate the Producer features "Position X" with keyframes or I would parent this feature to xPosition.
  
  I just don't know if this is possible and if so how?
  
  I invented this script...
  
  ```
      thisComp.layer("Blue").effect("CC Particle World")("Position X").transform("xPosition")
  
  ```
  
  it results in error!
  
  Thank you for your help.
  
  H.
  
  **Tags:** after-effects-expressions
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2015-05-26. Score: 3
  
  There's no property called `xPosition`, and `transform` is a property of a layer, not a method, but you're on the right track. The expression has to return an array of two values [x, y], and the components of the position are stored in an array like that too. The expression you want — if you're applying it to the layer position property — is this:
  
  ```js
  xpos=thisComp.layer("Blue").effect("CC Particle World")("Position X");
  ypos=transform.position[1];
  [xpos, ypos]
  
  ```
  
  That will apply the value of the `Position X` property of the effect to the **X** position of the layer, and the current **Y** value of the layer to the **Y**.
  
  If you're trying to use the layer's **X** position on the effect's Position **X** property then you need to use:
  
  ```js
  thisComp.layer("Blue").transform.position[0]
  
  ```
  
  you only need one value for this property.
  
  > **Pro Tip** a great way to learn how properties are accessed in expressions, as well as being a super quick and typo-free way of
  > creating them is to use the pickwhip. Next to the expression box
  > you'll see a curly icon. Click that and drag it to the property you
  > want to reference in your expression. So in the second case you could
  > drag it to the number for the **X** value of the layer's position and it
  > would give you the correct syntax for accessing it.
  >
  > ![enter image description here](https://i.sstatic.net/Z19IM.png)
  
  A good place to learn more about expressions is Dan Ebbert's page: <http://motionscript.com/>
  
  > **Comments:**
  > **username_2**: You're welcome, here is the meta: http://meta.video.stackexchange.com/questions/1449/syntax-highlighting, I hope we get a detailed explanation soon.  
  
  ---
  
  