To Right the Wrong V1

We'll say, plus three volts, when we go through this device, we get a voltage rise of three, then we get a voltage drop, because we go from plus to minus, we get a voltage drop of minus V1, and then we get another drop of V2, minus V2, equals zero.

That's our KVL equation for this circuit over here, so let's keep going with this analysis. Three volts, minus V1 is i times R1, i times 10, and V2 is i times 20 ohms, and that equals zero, so let's keep going. Three minus i times 10, plus 20, equals zero, and that means that i equals minus three over, minus three goes to this side, 10 plus 20 is 30, and the minus sign goes with the 30, minus 30, so i equals plus amp, so we solve for i, and let's just pick out V1.

Let's solve for V1, and we said earlier that V1 was i times R1, so V1 equals i, which is. If we do it for V2, that equals. That was a real quick analysis of a simple two resistor circuit, and we got all the voltages and currents. Now I'm going to go do the same thing again, but this time I'm going to do the voltage labels a little bit odd.

Your Answer

What I'm going to do here, is I'm going to say two plus. I'm going to define V1 to be in that direction, and we'll keep V2 like it was before, and now I need a current variable, and I'm going to call my current variable i here, just like we did before. Now at this point, you might say, Willie, you did it wrong. You did it wrong.

That's not the right voltage label, but I want to show you that I'm going to get the same answer, even though I did it this unusual way, so let's do the same KVL analysis on this circuit, and what I want to show you, is that the arithmetic that we're about to do takes care of the science just fine. All right, so KVL on this circuit says that we'll start at the same place, and go around the same direction, so this says they're three volts, a voltage rise of three volts, we go in the minus sign, and out the positive sign, so that's a voltage rise.

Now we get over to R1, and we go in the minus sign of R1, and out the plus sign, so that's plus V1, that's different than we had last time, right? Last time we had minus V1 here, see, and now we have plus V1. This is going to work out okay though. Now we go in the plus sign of V2, and we come out the minus sign, so that's a voltage drop, so we do a subtraction, and that equals zero.

API Versioning Has No “Right Way”

All right, we've got different equations, but we've got different definitions of V1, so now I want to write these V terms in terms of the resistance value, and the current value, and this is where we use the sign convention carefully, so now we need to include a term to represent R1, to use Ohm's law here. Now we have to be careful, this is one point we have to be careful, the current is going in the negative terminal of R1, so we're going to say VR1 equals negative i, times R1.

Does that make sense? If we define our current variable to be going in the negative sign, then Ohm's law picks up this negative sign, to make it come out right, so down here, we plug in minus iR1, which is minus i times 10, that's a difference, and then we go through V2, and V2 is the same as it was in the other equation, minus V2 is i times R2, which is 20, and that all equals zero.

Even right now, if you look at this equation, you see this minus sign, that snuck in here, because of our good use of the sign convention for passive componets. That makes this equation look just like this one here, so let's continue with the analysis.

Just need a little bit more room, three volts minus i times 10 plus 20, equals zero. Now we have the same equation as before, so we're going to get the same i, i equals, three goes to the other side, and becomes minus three, 10 plus 20 is 30, with the minus sign. One end-user application was producing errors like Error: This approach is very similar, but instead of versioning in the URL, versions go in the Accept and Content-Type headers.

The keeps the URL issue out of the way, and avoids API developers mistakenly sharing conventions in version specific base controllers.

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This is what many considered for a long time to be the height of API versioning myself included , and was the approach used by GitHub for a long time. It keeps the same endpoint working for a long time, but if the header is optional it can cause confusion. If v3 is added and v2 is eventually deprecated, clients would rather suddenly start getting a whole new version which might break their apps. Resource versioning does help, but can still be voodoo magic to many. This has all of the cons of the previously mentioned solutions, with a few more thrown in.

API Versioning Has No “Right Way” – APIs You Won't Hate

Primarily, that API developers get used to disposable endpoints. Disposable endpoint thinking has lead to situations where new update methods have been created that only contain subset of earlier update method functionality. Due to this divergence, even if a client wanted to upgrade, they could not! They are trapped on older versions, which then have to be supported forever, for fear of breaking the clients using the newer endpoint. This increased functionality is essentially asking all API teams to support more functionality than they should, and that is time and money that could be spent on more useful things.

API Evolution is the concept of never breaking your contracts until you absolutely absolutely have to, then when you do you manage that change with sensible warnings to clients. It is not about making arbitrary changes and breaking stuff. At a previous company offering crowdsourced carpooling , we only added fields, never removed them.

This was fine for the majority of changes, but when backwards compatible issues absolutely could not at all be avoided, we took advantage of the fact that a business name for a concept had changed, and took the chance to make our API match the business name.

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Matches were a relationship between a driver and a passenger, and multiple matches would make up the carpool. The BC change was to add multiple drivers, which completely screwed the concept of matches. After a few months, the matches concept was deprecated, and clients started using the new riders concept. The internals changed multiple times as we worked on recoding towards the new goal, and we converted matches to riders, then eventually matches was just a different serializer sat on top of riders.

During this process the contract never changed. The approach of evolution pushes some extra work onto the API development team, but avoids a similar amount of work being pushed onto the client teams. Whether you use Global URI Versioning, or want to use Evolution, you are going to need to consider how you handle deprecations. There are a few approaches to handling deprecations which you can use right now.

Deprecating Endpoints with Sunset. At WeWork we built a Faraday wrapper popular Ruby HTTP client called we-call that forces some good conventions onto client and server alike, using the power of middleware. One of those conventions is syntactic sugar around using the still-in-draft Sunset header , using annotations to make it super easy.