常规闭包参数

Question

this book 中出现了以下使用 grails 邮件插件提供的 sendMail 方法的示例.

sendMail {
    to "foo@example.org"
    subject "Registration Complete"
    body view:"/foo/bar", model:[user:new User()]
}

我知道 {} 中的代码是一个作为参数传递给 sendMail 的闭包。我也明白 to , subject和 body是方法调用。

我试图弄清楚实现 sendMail 方法的代码是什么样的，我最好的猜测是这样的:

MailService {

    String subject
    String recipient
    String view
    def model

    sendMail(closure) {
        closure.call()
        // Code to send the mail now that all the 
        // various properties have been set
    }

    to(recipient) {
        this.recipient = recipient
    }

    subject(subject) {
        this.subject = subject;
    }

    body(view, model) {
        this.view = view
        this.model = model
    }
}

这是合理的，还是我错过了什么？特别是闭包中调用的方法( to 、 subject 、 body )是否必须与 sendMail 属于同一类的成员？ ?

谢谢，
大学教师

Answer 1

MailService.sendMail 闭包委托(delegate):

 MailMessage sendMail(Closure callable) {
    def messageBuilder = new MailMessageBuilder(this, mailSender)
    callable.delegate = messageBuilder
    callable.resolveStrategy = Closure.DELEGATE_FIRST
    callable.call()

    def message = messageBuilder.createMessage()
    initMessage(message)
    sendMail message
    return message
}

例如，MailMessageBuilder 的方法:

void to(recip) {
    if(recip) {
        if (ConfigurationHolder.config.grails.mail.overrideAddress)
            recip = ConfigurationHolder.config.grails.mail.overrideAddress
        getMessage().setTo([recip.toString()] as String[])
    }
}