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# SecTransformPushbackAttribute(_:_:_:)

Pushes a single value back for a specific attribute.

```
func SecTransformPushbackAttribute(_ ref: SecTransformImplementationRef, _ attribute: SecTransformStringOrAttribute, _ value: CFTypeRef) -> CFTypeRef?
```

## Parameters

`ref`

A [`SecTransformImplementationRef`](/documentation/Security/SecTransformImplementationRef) that is bound to an instance of a custom transform.

`attribute`

The name or the attribute handle of the attribute whose value is to be pushed back. When using a name, see [Transform Attributes](/documentation/Security/transform-attributes) for a list of valid key names.

`value`

The value being pushed back.

## Return Value

An error on failure, or `NULL` on success. In Objective-C, call the <doc://com.apple.documentation/documentation/CoreFoundation/CFRelease> function to free the error’s memory when you are done with it.

## Discussion

Calling this function stops the flow of data into the specified attribute until any attribute is changed for the transform instance bound to the `ref` parameter.

---

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