---
title: "index(of:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/nsarray/index(of:)"
---

# index(of:)

Returns the lowest index whose corresponding array value is equal to a given object.

## Declaration

```swift
func index(of anObject: Any) -> Int
```

## Parameters

- `anObject`: An object.

## Return Value

Return Value The lowest index whose corresponding array value is equal to anObject. If none of the objects in the array is equal to anObject, returns NSNotFound.

## Discussion

Discussion Starting at index 0, each element of the array is passed as an argument to an isEqual(_:) message sent to anObject until a match is found or the end of the array is reached. Objects are considered equal if isEqual(_:) (declared in the NSObjectProtocol protocol) returns true.

## See Also

### Related Documentation

- [contains(_:)](foundation/nsarray/contains(_:).md)

### Finding Objects in an Array

- [index(of:in:)](foundation/nsarray/index(of:in:).md)
- [indexOfObjectIdentical(to:)](foundation/nsarray/indexofobjectidentical(to:).md)
- [indexOfObjectIdentical(to:in:)](foundation/nsarray/indexofobjectidentical(to:in:).md)
- [indexOfObject(passingTest:)](foundation/nsarray/indexofobject(passingtest:).md)
- [indexOfObject(options:passingTest:)](foundation/nsarray/indexofobject(options:passingtest:).md)
- [indexOfObject(at:options:passingTest:)](foundation/nsarray/indexofobject(at:options:passingtest:).md)
- [indexesOfObjects(passingTest:)](foundation/nsarray/indexesofobjects(passingtest:).md)
- [indexesOfObjects(options:passingTest:)](foundation/nsarray/indexesofobjects(options:passingtest:).md)
- [indexesOfObjects(at:options:passingTest:)](foundation/nsarray/indexesofobjects(at:options:passingtest:).md)
- [index(of:inSortedRange:options:usingComparator:)](foundation/nsarray/index(of:insortedrange:options:usingcomparator:).md)