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By the way, here's a GIF of what the buying process looks like: https://gfycat.com/BleakSimilarGermanspaniel https://gfycat.com/BleakSimilarGermanspaniel This

by shazow 9y ago

By the way, here's a GIF of what the buying process looks like: https://gfycat.com/BleakSimilarGermanspaniel https://gfycat.com/BleakSimilarGermanspaniel This is the part that blows my mind, it feels like magic every time. (P.S. Thanks for your support, Chris!)

billmalarky 9y ago
Payment as part of the protocol alone will make DAPPs a game changer.
eridius 9y ago
That GIF is neat, but I don't see your ad when I look at the page.
- drampelt 9y ago
  It looks like they did it on the Rinkeby Testnet for that demo so they wouldn't have to spend real Ether.
sturmeh 9y ago
Wait so how/where is the url/title/image stored? (I assume it's a url?) I notice you buy it then you later change the details?
- baby 9y ago
  it's stored on the blockchain, inside the transaction that calls the payable function. The setup is done in two steps: 1. you must pay for a rectangle area via the `buy` function (notice the `payable` specifier): function buy(uint _x, uint _y, uint _width, uint _height) payable returns (uint idx) { 2. then you can setup your ad via the publish function: function publish(uint _idx, string _link, string _image, string _title, bool _NSFW) { ~~~ For more details in 1: * the cost of the area you're trying to buy is calculated as _width * _height * pixelsPerCell * weiPixelPrice * with weiPixelPrice = 1000000000000000 and pixelsPerCell = 100 * The grid is defined as a double array of 100x100: bool[100][100] public grid; * The for loop checks that none of these pixels are set to true, if any pixel is then `revert` reverts any changes to the state that happened during execution. Otherwise the relevant coordinates are all set to true. * The space is reserved under the address that send the ether (`msg.sender`). To do that, an `Ad` struct is filled with the information and it is pushed unto the state. Ad memory ad = Ad(msg.sender, _x, _y, _width, _height, "", "", "", false, false); idx = ads.push(ad) - 1; * It returns an index (`Idx`) that you can use to specify the details of your ad later. ~~~ For more details in 2: * You must pass the `index` of your reserved space as argument to the function * It will check that your address is indeed the address which reserved the space: require(msg.sender == ad.owner); * It sets everything to the arguments of the function you're calling. * An event is triggered, it is probably being listened to by the web app so that the web page can be updated live Publish(_idx, ad.link, ad.image, ad.title, ad.NSFW || ad.forceNSFW); ~~~ Notes: * Looks like you can call the `publish` function over and over. Modifying your ad over and over. * There is a `forceNSFW` function that the contract owner can use to force an ad to have the `NSFW` flag. But this can be re-modified again and again by the ad owner. * But the owner of the contract can remove ownership of an Ad, so there's that. * I just audited the contract and I couldn't find any vulnerability.

by shazow 9y ago

billmalarky 9y ago

Payment as part of the protocol alone will make DAPPs a game changer.

eridius 9y ago

That GIF is neat, but I don't see your ad when I look at the page.

drampelt 9y ago
It looks like they did it on the Rinkeby Testnet for that demo so they wouldn't have to spend real Ether.

sturmeh 9y ago

Wait so how/where is the url/title/image stored? (I assume it's a url?) I notice you buy it then you later change the details?

baby 9y ago
it's stored on the blockchain, inside the transaction that calls the payable function. The setup is done in two steps: 1. you must pay for a rectangle area via the `buy` function (notice the `payable` specifier): function buy(uint _x, uint _y, uint _width, uint _height) payable returns (uint idx) { 2. then you can setup your ad via the publish function: function publish(uint _idx, string _link, string _image, string _title, bool _NSFW) { ~~~ For more details in 1: * the cost of the area you're trying to buy is calculated as _width * _height * pixelsPerCell * weiPixelPrice * with weiPixelPrice = 1000000000000000 and pixelsPerCell = 100 * The grid is defined as a double array of 100x100: bool[100][100] public grid; * The for loop checks that none of these pixels are set to true, if any pixel is then `revert` reverts any changes to the state that happened during execution. Otherwise the relevant coordinates are all set to true. * The space is reserved under the address that send the ether (`msg.sender`). To do that, an `Ad` struct is filled with the information and it is pushed unto the state. Ad memory ad = Ad(msg.sender, _x, _y, _width, _height, "", "", "", false, false); idx = ads.push(ad) - 1; * It returns an index (`Idx`) that you can use to specify the details of your ad later. ~~~ For more details in 2: * You must pass the `index` of your reserved space as argument to the function * It will check that your address is indeed the address which reserved the space: require(msg.sender == ad.owner); * It sets everything to the arguments of the function you're calling. * An event is triggered, it is probably being listened to by the web app so that the web page can be updated live Publish(_idx, ad.link, ad.image, ad.title, ad.NSFW || ad.forceNSFW); ~~~ Notes: * Looks like you can call the `publish` function over and over. Modifying your ad over and over. * There is a `forceNSFW` function that the contract owner can use to force an ad to have the `NSFW` flag. But this can be re-modified again and again by the ad owner. * But the owner of the contract can remove ownership of an Ad, so there's that. * I just audited the contract and I couldn't find any vulnerability.