decideAction(for:completionHandler:)
Determines the action that the system takes when it downloads a message.
Declaration
func decideAction(for message: MEMessage, completionHandler: @escaping @Sendable (MEMessageActionDecision?) -> Void)func decideAction(for message: MEMessage) async -> MEMessageActionDecision?Parameters
- message:
The message the system downloads.
- completionHandler:
A block you call that indicates the action to perform on the message, or if MailKit should invoke this method again after it downloads the message content.
Discussion
As MailKit downloads messages, it invokes this method to determine what action, if any, it should perform on the message. MailKit initially calls this method before downloading the message content. If you can determine the action to take without requiring the entire body, create a MEMessageActionDecision with an MEMessageAction that indicates the action to take. Use the properties of message to determine the action to take. For example, if the user chooses to set the color of messages from a particular person, use the message’s fromAddress property.
If you can’t determine the action without the entire message content and bodyData is nil, call the completion handler and pass invokeAgainWithBody as the decision. MailKit invokes this method again later after the bodyData in the message is available.
The following code shows an implementation that sets the color of all messages with Project Mars in the subject to red. Because this example only relies on the subject of the message, it calls the completion handler with an action immediately.
func decideActionForMessage(for message: MEMessage, completionHandler: @escaping (MEMessageActionDecision?) -> Void) {
var action: MEMessageActionDecision? = nil
// Check if the subject of the email is about Project Mars.
if message.subject.contains("Project Mars") {
// Create an action to set the color of the
// message in the message list to red.
action = MEMessageActionDecision.action(.setColorActionWith(.red))
}
// Call the completion handler with the action, if any.
completionHandler(action)
}The next example shows a different implementation that relies on the message body content to determine if a message is junk. In this case, when bodyData is nil, the handler calls the completion handler and passes invokeAgainWithBody.
When MailKit downloads the message content, it invokes this method again. This time, the handler converts the body data to a string. If the string indicates that the message is junk, the handler calls the completion handler passing an action that moves the message to the user’s Junk mailbox.
func decideActionForMessage(for message: MEMessage, completionHandler: @escaping (MEMessageActionDecision?) -> Void) {
var action: MEMessageActionDecision? = nil
// Check if the message content is available.
if message.bodyData == nil {
// If it isn't, request a repeat call when it is.
action = MEMessageActionDecision.invokeAgainWithBody
} else if let bodyData = message.bodyData,
let body = String(data: bodyData, encoding: .utf8){
// Determine if the message is junk or not.
let isJunk = body.contains("Make money fast!")
// If it is, then call the completion handler with an action
// to move the message to the Junk mailbox.
if isJunk {
action = MEMessageActionDecision.action(.moveToJunk)
}
}
// Call the completion handler with the action, if any.
completionHandler(action)
}