How to use $A.set() or how to add a custom global value provider?

Question

I am a little bit confused. Knowing that not all features which are available in a pure aura project are exposed to Lightning Components I thought it is mandatory to check against the Salesforce developer documentation.

So in the auradocs/reference.app below the JavaScript API section I found the function $A.set() giving this example:

$A.set("$Custom.something","new Value")

Unfortunately this does not work, giving me an error "Unable to set value for key". So my assumption is that I have to define a global value provider with the appropriate key first. When you search the Salesforce developer documentation against global value provider you get the first result showing up:

https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/expr_global_value_providers_custom.htm?search_text=global%20value%20provider

It seems that the search result is not within the scope of the Lightning Components as it does not show up in the navigation.

Does anyone have an idea how

• $A.set() is working
• I can add a custom global value provider or any other mechanism to store data in a manner known as Singleton

Thanks in advance

Chris

Answer 1

$A.set() isn't exposed in Lightning Experience.

You can check this blog post re: client-side shared singleton (across components):

https://developer.salesforce.com/blogs/developer-relations/2016/12/lightning-components-code-sharing.html

Answer 2

Take note of and read the pink section at the bottom of that page I pointed you to earlier in my comments. You can't use a string like 'Hello {0}' to tell it what to set the v attribute with. Instead, you must use an expression like $Label.mySection.salutation.

What you're doing is using that expression to tell Lightning (using object oriented expressions) how it should assign values to your v attributes. You're approaching it from the opposite direction by setting $Label.mySection.salutation to Hello {0}. That's how you accomplish what you want to do. Change the value assigned to $Label.mySection.salutation and you'll get a different behavior/result in your component.