Ivars

@dynamicMemberLookup
public struct Ivars<IvarType>

A wrapper around an object for accessing ivars on it.

This type supports dynamic member lookup, which means that ivars can be accessed as if they were members of the type. Note that if an ivar with the given name does not exist, the dynamic member access will result in a crash.

To access a pointer to the ivar instead, use Ivars.withIvar(_:_:).
To fail gracefully if the ivar does not exist, use Ivars.subscript(safelyAccessing:).
To access an ivar with a name that clashes with an actual member on this type, it is possible to use Ivars.subscript(dynamicMember:) directly.

Example

let object = MyObject(foo: 5)
Ivars<Int>(object)._foo // 5
Ivars(object)._foo = 7
print(object.foo) // 7

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                    init(_:)

Construct a new instance of Ivars for accessing instance variables on object.

Declaration

Swift

public init(_ object: AnyObject)

Parameters


                                object

The object on which ivars are to be accessed.

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                    withIvar(_:_:)

Access an instance variable on the object.

It is safe to assume that body will be called on all execution paths.

Warning

The pointer argument should not be stored and used outside of the lifetime of the call to the closure.

Declaration

Swift

public func withIvar<Result>(
    _ name: String,
    _ body: (_ pointer: UnsafeMutablePointer<IvarType>?) throws -> Result
) rethrows -> Result

Parameters

`name`	The name of the instance variable to access.
`body`	A block which receives a pointer to the ivar, within which it may be read or written to.
`pointer`	The pointer to the ivar, or `nil` if `object` does not have an ivar with the provided `name`.

Return Value

The value returned from body.

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                    subscript(safelyAccessing:)

Access an instance variable on the object, failing gracefully if the instance variable does not exist.

Note

If the setter is passed a value of nil, it will do nothing.

Declaration

Swift

public subscript(safelyAccessing ivarName: String) -> IvarType? { get nonmutating set }

Parameters


                                ivarName

The name of the instance variable to access.

Return Value

The value of the instance variable, or nil if there is no ivar with the given name.

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                    subscript(dynamicMember:)

Access an instance variable on the object.

Precondition

The ivar ivarName must be present on the object. If an ivar with the given name is not present, using this subscript will result in a crash.

To fail gracefully, use Ivars.subscript(safelyAccessing:) or Ivars.withIvar(_:_:).

Declaration

Swift

public subscript(dynamicMember ivarName: String) -> IvarType { get nonmutating set }

Parameters


                                ivarName

The name of the instance variable to access.

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