Apply a directive conditionally

I am using Material 2 to add md-raised-button. I want to apply this directive only if certain condition becomes true.

For example:

<button md-raised-button="true"></button>

Another example: I created a basic dynamic reactive form in plunker. I am using formArrayName directive of reactive form for array of controls. I want to apply formArrayName directive only if specific condition becomes true, otherwise don't add formArrayName directive.

Here is a plunker link.

If you just need to add an attribute in order to trigger CSS rules, you can use the below method: (this does not dynamically create/destroy a directive)

<button [attr.md-raised-button]="condition ? '' : null"></button>

Applied the same to your plunker: fork

Update:

How condition ? '' : null works as the value:

When its the empty string ('') it becomes attr.md-raised-button="", when its null the attribute will not exist.

Update: plunker update: fork (version issues fixed, please note the question was originally based on angular 4)

I don't know if you can apply directives based on a condition, but a workaround would be having 2 buttons and display them based on a condition.

<button *ngIf="!condition"></button>
<button *ngIf="condition" md-raised-button></button> 

Edit: maybe this will be helpful.