Rust
Using Replace Patterns in Email

Demonstrates how to use the replace patterns (mail-merge) feature in Chilkat MailMan.
Chilkat Rust Downloads

Rust

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// ---------------------------------------------------------------------
// Create an email template for sending.
let email_template = chilkat::Email::new();

// We're going to replace "FIRST_NAME" with an actual name.
// We arbitrarily chose "FIRST_NAME".  We can choose anything, such as "CUSTOMER_NAME" or "THE_RECIPIENT_NAME"...
email_template.set_subject("Hello FIRST_NAME,");

email_template.set_from("john@example.com");
let _ = email_template.add_to("FIRST_NAME", "RECIPIENT_EMAIL");

email_template.set_html_body("<html><body><h2>Hello FIRST_NAME,</h2><p>Your order for PRODUCT_NAME has been shipped.</p></body></html>");

// If the email is saved to a file, we can see what it contains:
let _ = email_template.save_eml("qa_output/emailTemplate.eml");

// For example:

// MIME-Version: 1.0
// Date: Tue, 26 Apr 2022 07:10:52 -0500
// Message-ID: <715CF231A9F07B0B9FDB073518CD94138D791866@XYZ>
// Content-Type: text/html; charset=us-ascii
// Content-Transfer-Encoding: 7bit
// X-Priority: 3 (Normal)
// Subject: Hello FIRST_NAME,
// From: john@example.com
// To: FIRST_NAME <RECIPIENT_EMAIL>
// 
// <html><body><h2>Hello FIRST_NAME,</h2><p>Your order for PRODUCT_NAME has been shipped.</p></body></html>

// ---------------------------------------------------------------------
// Demonstrate replace patterns by setting and then rendering to MIME.

let mailman = chilkat::MailMan::new();

let _ = email_template.set_replace_pattern("FIRST_NAME", "Elon");
let _ = email_template.set_replace_pattern("RECIPIENT_EMAIL", "elon.musk@example.com");
let _ = email_template.set_replace_pattern("PRODUCT_NAME", "Twitter Corporation");

// Render to MIME to see what we get.
// Note: When the MailMan sends an email, it renders the email to MIME and then sends.
// The rendering process is to do replacements, or possibly sign, encrypt, etc.
// When MailMan.SendEmail is called, internally the email is rendered, and the rendered email is sent.
// The equivalent to MailMan.Send email is to call email.RenderToMime followed by MailMan.SendMime.
let mime = mailman.render_to_mime(&email_template).unwrap_or_default();
println!("{}", mime);

// This is the rendered MIME:

// MIME-Version: 1.0
// Date: Tue, 26 Apr 2022 07:25:49 -0500
// Message-ID: <750582BCDC891C67B48CEE2293C08B902C3891E9@XYZ>
// Content-Type: text/html; charset=us-ascii
// Content-Transfer-Encoding: 7bit
// X-Priority: 3 (Normal)
// Subject: Hello Elon,
// From: john@example.com
// To: Elon <elon.musk@example.com>
// 
// <html><body><h2>Hello Elon,</h2><p>Your order for Twitter Corporation has been shipped.</p></body></html>

// Note: When rendering, the Date and Message-ID headers are automatically regenerated.

// ---------------------------------------------------------------------
// An application can see what replacement patterns it previously set by calling SetReplacePattern multiple times.
let mut count = email_template.num_replace_patterns();
println!("Number of replace patterns: {}", count);

let mut i = 0;
while i < count {
    // Note: The GetReplaceString method was found to not be working correctly.  It was returning the same value as GetReplacePattern.
    // It is fixed in Chilkat v9.5.0.91
    println!("{}: {}", email_template.get_replace_pattern(i).unwrap_or_default(), email_template.get_replace_string(i).unwrap_or_default());
    i = i + 1;
}

// Or lookup a replacement pattern by name:
let name = "FIRST_NAME".to_string();
println!("{} = {}", name, email_template.get_replace_string2(&name).unwrap_or_default());

// Sample output:

// Number of replace patterns: 3
// FIRST_NAME: Elon
// RECIPIENT_EMAIL: elon.musk@example.com
// PRODUCT_NAME: Twitter Corporation
// FIRST_NAME = Elon

// ---------------------------------------------------------------------
// Finally... demonstrate sending emails using the replacement patterns.
// 

// Set our mail server settings..
mailman.set_smtp_host("smtp.mail.us-west-2.awsapps.com");
mailman.set_smtp_ssl(true);
mailman.set_smtp_port(465);

mailman.set_smtp_username("john@example.com");
mailman.set_smtp_password("the_password");

// Imagine we have data in JSON format, and we wish to send the templated email to each recipient...
// 

// {
// 	"mail_merge" : [
// 		{
// 			"to": "mary@example.com",
// 			"name": "Mary",
// 			"product": "Widget 1" 
// 		},
// 		{
// 			"to": "robert@example.com",
// 			"name": "Robert",
// 			"product": "Widget 2"
// 		}	
// 		...
// 	]
// }

let json = chilkat::JsonObject::new();
if json.load_file("qa_data/json/mail_merge.json").is_err() {
    println!("{}", json.last_error_text());
    return;
}

let mut email_addr = String::new();
let mut first_name = String::new();
let mut product = String::new();

i = 0;
count = json.size_of_array("mail_merge");
while i < count {
    json.set_i(i);
    email_addr = json.string_of("mail_merge[i].to").unwrap_or_default();
    first_name = json.string_of("mail_merge[i].name").unwrap_or_default();
    product = json.string_of("mail_merge[i].product").unwrap_or_default();

    let _ = email_template.set_replace_pattern("FIRST_NAME", &first_name);
    let _ = email_template.set_replace_pattern("RECIPIENT_EMAIL", &email_addr);
    let _ = email_template.set_replace_pattern("PRODUCT_NAME", &product);

    if mailman.send_email(&email_template).is_err() {
        println!("{}", mailman.last_error_text());
        return;
    }

    println!("Send email to {}", email_addr);

    i = i + 1;
}

println!("Success.");