Money Makes Your App Go Round

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We Are Experiencing An Introduction Please Stand By Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I've made some mistakes Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Once upon a time... Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I got a new client Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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They wanted to add complex payment logic to an existing payment gateway connection Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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The API call already existed I thought the hard part was done Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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(Spoiler Alert) The API call isn't the hard part Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Money Makes Your App Go Round Noel Rappin, Table XI (@noelrap) Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Some context Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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token = params[:stripeToken] begin charge = Stripe::Charge.create( amount: 1000, currency: "usd", source: token, description: "Example charge") rescue Stripe::CardError => e # The card has been declined end Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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The resulting transaction involves at least ! institutions Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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As many as 1,000,000 per minute Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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But then there's this: Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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validates :last_4, format: {with: /X{12}\d{4}/} Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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There's a really common pattern Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Save some data Charge the card Save the response Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Charge Fails Save Succeeds Angry Manager! Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Charge Succeeds Save Fails Angry Customer! Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Back to validates :last_4, format: {with: /X{12}\d{4}/} Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Every line of code after the card processes is a potential angry customer Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Is this validation really necessary? Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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PragDave: "screw up in favor of the customer" Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Mitigating failure Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Test failure conditions Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Testing for credit card failures is actually pretty easy Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Testing for local failures is trickier Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Foreign key constraints are useful, but irritating Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Small background jobs are great Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Idempotence is your friend Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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It is often easier to see the result of bugs than to find the cause Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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An ounce of mitigation can be worth a pound of bug fixing Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Money is precise Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Money is so precise that it breaks math Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Okay, it just breaks floating point numbers Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Use the Money gem to store money as BigDecimal Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Money requires records Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Handling Fee: $2.00 Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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It's a constant HANDLING_FEE: 200 Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Later... Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Change the constant HANDLING_FEE: 250 Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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And we're done... Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Except for the past Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Store all your partial results Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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You should be able to recreate the entire purchase even if the logic has changed Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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If there is failure, keep a record of the failure Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Audit changes Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Check your data Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Money has legal obligations Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Take your administrative users seriously Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Pragmatic's admin code is 2x the size of the main app Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Admins can change rules which makes them complicated Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Example: Refunds Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Refunds are a one-line API call Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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But: 4 Who can authorize one? 4 Full or partial? 4 How to manage response? 4 How to track inventory 4 How to track changes to revenue? 4 Etc.. Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Take Reporting Seriously (I didn't) Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Reporting is how you make business decisions Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Taxes security requirements financial system compliance Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Money is Private Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Don't store personal information that you don't need Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Don't store credit card info Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Even seemingly boring information can be harmful Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Takeaways Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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The API is the easy part Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Run in small steps to manage potential failure points Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Store all your work Store as little personal info as you can Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Administration is important Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Noel Rappin (@noelrap) Table XI http://pragprog.com/book/ nrwebpay http://www.noelrappin.com/trdd http://pragprog.com/book/ Noel Rappin, Money Makes Your App Go Round, WindyCityRails 2016. http://www.noelrappin.com | http://www.tablexi.com | @noelrap