Struct design_pattern_examples_rust::memento::MementoContext

struct MementoContext {
    undo_list: Vec<Memento>,
}

This struct creates a context around the undo list that the memento_exercise() executes within. This gets around the problem of needing a static undo list as all the methods on this context have ready access to the undo list in the context.

Fields

undo_list: Vec<Memento>

The list of memento objects that form a series of snapshots in time of a MementoTextObject.

Implementations

impl MementoContext

fn new() -> MementoContext

Constructor.

fn save_for_undo(&mut self, text_object: &MementoTextObject, operation: &str)

Take a snapshot of the given text object associated with the name of given operation.

Parameters

• text_object

  The MementoTextObject to take a snapshot of.

• operation

  A string describing the operation that will be applied after the snapshot is taken.

fn operation_replace( &mut self, text_object: &mut MementoTextObject, search_pattern: &str, replace_text: &str )

An operation to search and replace text in a MementoTextObject.

Parameters

• text_object

  The MementoTextObject to work with.

• search_pattern

  What to look for in the MementoTextObject

• replace_text

  What to replace the search_pattern with

fn operation_reverse(&mut self, text_object: &mut MementoTextObject)

An operation to reverse the characters in the given MementoTextObject.

Parameters

• text_object

  The MementoTextObject to work with.

fn undo(&mut self, text_object: &mut MementoTextObject)

Perform an undo on the given Command_TextObject, using the mementos in the “global” undo list. If the undo list is empty, nothing happens.

Parameters

• text_object

  The MementoTextObject to update.

fn apply_replace_operation( &mut self, text_object: &mut MementoTextObject, search_pattern: &str, replace_text: &str )

Helper function to replace a pattern with another string in the given MementoTextObject after adding a snapshot of the text object to the undo list. Finally, it shows off what was done.

Parameters

• text_object

  The MementoTextObject to update.

• search_pattern

  What to look for in the MementoTextObject

• replace_text

  What to replace the search_pattern with

fn apply_reverse_operation(&mut self, text_object: &mut MementoTextObject)

Helper function to reverse the order of the characters in the given MementoTextObject after adding a snapshot of the text object to an undo list. Finally, it shows what was done.

Parameters

• text_object

  The MementoTextObject to work with.