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This repository was archived by the owner on Dec 3, 2021. It is now read-only.

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Minting tokens, part 2
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‎tutorial/1-workspace.md

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Before starting, it's important to have setup correctly our workspace. You can follow the steps described in the [documentation](https://embark.status.im/docs/), since it will always be updated to reflect latest changes in the framework. If you already have Embark and its dependencies installed you can skip this step.
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At the moment of writing the tutorial, the commands I used on Ubuntu 18.04 were these. Some steps change depending on the operative system used (i.e. [node-gyp](https://github.com/nodejs/node-gyp)), as well as the versions of files. Please refer to Embark or any of the installed tools' documentation website for troubleshooting.
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At the moment of writing the tutorial, the commands I used on Ubuntu 18.04 were these. Some steps change depending on the operative system used (i.e. [node-gyp](https://github.com/nodejs/node-gyp)), as well as the versions of files. Please refer to Embark or any of the installed tools' documentation website for troubleshooting. Also a docker image is being built with Embark and all its dependencies, and it may be used to follow this tutorial.
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## Ubuntu Installation
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### NodeJS 9.8.0 (lts) with nvm 0.33.11
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```

‎tutorial/2-minting-tokens.md

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@@ -83,15 +83,74 @@ EmbarkJS.Storage.uploadFile(this.state.fileToUpload)
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```
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#### Using our contract to mint the new token
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Finally, once we have both the Image and the Attributes stored in IPFS it's time to mint our new token. This is done in two steps: first, we estimate the gas cost to invoke the `mint(bytes _metadataHash, uint8 _energy, uint8 _lasers, uint8 _shield, uint _price) public onlyOwner` (it's a good practice, in order to avoid running into Out of Gas exceptions), and then, we will create the transaction. To estimate gas, we use the estimateGas() function of the contract:
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```
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const { mint } = SpaceshipToken.methods;
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let toSend;
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EmbarkJS.Storage.uploadFile(this.state.fileToUpload)
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.then(fileHash => {
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attributes.image = 'https://ipfs.io/ipfs/' + fileHash;
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return EmbarkJS.Storage.saveText(JSON.stringify(attributes))
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})
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.then(attrHash => {
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toSend = mint(web3.utils.toHex(attrHash),
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this.state.energy,
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this.state.lasers,
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this.state.shield,
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web3.utils.toWei(this.state.price, "ether"));
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return toSend.estimateGas();
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})
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.then(estimatedGas => {
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console.log(estimatedGas);
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})
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.catch((err) => {
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console.error(err);
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})
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.finally(() => {
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this.setState({isSubmitting: false});
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});
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```
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Notice that we stored the function call in the `toSend` variable, however it does not mean that we're creating a transaction here. With this `toSend` variable we're able to send a transaction or estimating gas (also, calling a value if the contract function were a `constant`/`view`/`pure` function).
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Also, we introduced the use of two `web3.utils` functions: `toHex`, to convert any given value to a HEX string, and also, `toWei`, to convert from ether to wei, since in the UI we're introducing the values as ether, and the smart contract uses wei.
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After estimating gas, we proceed to create the transaction by returning the `send` method of our contract with the estimated gas plus an additional wei amount (estimateGas() is not always precise).
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```
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...
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...
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.then(estimatedGas => {
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return toSend.send({gas: estimatedGas + 1000});
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})
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.then(receipt => {
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console.log(receipt);
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// Reset form
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this.setState({
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fileToUpload: [],
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energy: '',
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lasers: '',
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shield: '',
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price: ''
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});
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this.props.loadShipsForSale();
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})
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...
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...
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```
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Notice that `send()` returns a promise, and when it resolves, you can access a receipt object with all the information about the transaction as well as logs generated. Here we also clean the form, and invoke `this.props.loadShipsForSale()` to reload the list of ships. It doesn't do anything at the moment since we haven't implemented it yet.
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We did not implement success/error alert messages or warnings to the user. These can be added inside the promise resolution and catch blocks.
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### Full implementation of the handleClick(e) function:
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```
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handleClick(e){
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e.preventDefault();
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const { mint } = SpaceshipToken.methods;
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this.setState({isSubmitting: true});
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}
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}
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const { mint } = SpaceshipToken.methods;
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let toSend;
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EmbarkJS.Storage.uploadFile(this.state.fileToUpload)
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return toSend.estimateGas();
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})
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.then(estimatedGas => {
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return toSend.send({from: web3.eth.defaultAccount,
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gas: estimatedGas + 1000});
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return toSend.send({gas: estimatedGas + 1000});
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})
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.then(receipt => {
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console.log(receipt);
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shield: '',
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price: ''
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});
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this.props.loadShipsForSale();
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return true;
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})
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.catch((err) => {
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console.error(err);

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