I'm aware that we can integrate in-app purchases with storekit. but i want to integrate payments using credit card. will apple allow to integrate such libraries? Are there any such libraries available where users can use their credit card for payment of products with in my app?
Depending on what users are purchasing*, you should be just fine accepting payments in your app. Instead of trying to incorporate some type of payment library into the app I would recommend using a payment API that offloads the work. Take a look at http://stripe.com/ for an example of an excellent payment system designed for ease of integration. Their API reference even mentions integration with iPhone apps.
*If you are trying to sell features or services of the app itself you will almost definitely be running afoul of Apple's guidelines, but based on the fact that you said "products" I am assuming this is not the case. In fact, while you must use the in-app purchase system for "content, functionality, or services in an app" you are specifically forbidden from using it for "physical goods or goods and services used outside of the application" (item 11.3 of Apple's App Store Review Guidelines).
Apple does allow not Apple's IAP in-app payments for goods not consumed in the phone (Digital content) as stated above. See this example of an approved app that use external library for accepting credit cards in their app: iStash
In my opinion Stripe is good solution but not the ideal for in-app as it is a web based solution and focuses on web experience.
If you want a true mobile in-app experience I suggest you check out PayPal library or my company, ZooZ, which accepts both PayPal and Credit Cards in one integration.
working project can be find here on github stripe example.
As an iOS dev you'd best have a good read through this. Specifically pertinent to you is section 11.2:
11.2 Apps utilizing a system other than the In App Purchase API (IAP) to purchase content, functionality, or services in an app will be rejected
They want the profit, and they get their cut if you use the IAP API. Hope that clears up any issues.
EDIT: I am assuming based on the wording of your question that the payment will unlock something transitory in the app. IAP are only appropriate when purchasing something digital. If what you are selling is physically tenable, then you shouldn't, and in fact are not allowed, to use the IAP API. In that case, something along the lines of Stripe or a web-based version of Paypal's API would work.
In support of David's answer, I would like to add that, using a payment API to accept payments for products/donation through your app would be ideal.
Apple Pay is now available (as of today) on iPhone 6 and 6 Plus, and active only in US.
But if you still want to add support in your app for devices that cannot use Apple Pay, Authorize.Net now has an iOS SDK which you can use to integrate and enable credit card payments.
来源：https://stackoverflow.com/questions/8762096/ios-integrating-credit-card-payments