Question: I am using DynamoDBMapper to insert a new object to my table.
Table structure:

```
key: hash_key
attribute1: global sec index
other attributes

```

Now i want the value of attribute1 to be unique in the table. How to do that?

Already tried:

```
a. map.put("attribute1", new ExpectedAttributeValue(false));
b. map.put("atrribute1", new ExpectedAttributeValue().withExists(false));

```

I am using `mapper.save()` with default SaveBehaviour.

Answer: 
Dot `.` is use for `concatenate`. You use `->` to access member of class

```
$result = $mailer->SendMail();

```
`.` is a contact operator, to access member of a class both variable and functions use `->` operator
use the below code:  

`$result = $mailer->SendMail();`