[英]Chained and Nested promises with For Loop
我試圖使我的游戲的每個屬性都處於鏈式承諾中(每個屬性都來自不同的異步調用)。
我的算法邏輯:
碼:
var games = [];
window.addEventListener('load', function() {
// Check the Network and assign the smart contract address
web3.eth.net.getId()
.then(function(networkId) {
let contractAddressRegistry;
if (networkId == 1) {
contractAddressRegistry = "0xQWERTYUIOPQWERTYUIOPQWERTY"
} else {
contractAddressRegistry = "0x12345678901234567890123456"
}
return contractAddressRegistry;
})
.then(function(contractAddressRegistry) {
let contractRegistry = new web3.eth.Contract(contractAbiRegistry, contractAddressRegistry);
contractRegistry.methods.numberOfGames().call()
.then(function(numberOfGames) {
for (let i = 0; i < numberOfGames; i++) {
let game = {};
game.propertyA = aSyncCallGetPropertyA(i); // Promise
game.propertyB = aSyncCallGetPropertyB(i); // Promise
game.propertyC = aSyncCallGetPropertyC(i); // Promise
}
games.push(game);
})
})
.then(function() {
console.log(games) // Empty
})
})
我嘗試使用Promises.all(),但由於在then()中有一些異步調用,因此我無法正確同步它。
如何確保讓對象游戲充滿其所有屬性?
您應該這樣使用Promise.all
。 基本上,您需要將所有三個aSyncCallGetProperty
異步調用都包裝在Promise.all
,等待它們真正完成,然后將結果分配給對象game
。
whatever
.then(function(contractAddressRegistry) {
let contractRegistry = new web3.eth.Contract(contractAbiRegistry, contractAddressRegistry);
return contractRegistry.methods.numberOfGames().call();
})
.then(function(numberOfGames) {
return Promise.all(numberOfGames.map(() => {
return Promise.all([
aSyncCallGetPropertyA(),
aSyncCallGetPropertyB(),
aSyncCallGetPropertyC()
]).then(results => {
let game = {};
game.propertyA = results[0];
game.propertyB = results[1];
game.propertyC = results[2];
return game;
});
}));
})
.then(function(games) {
console.log(JSON.stringify(games));
})
@Lewis的代碼似乎正確,但我無法確定numberOfGames
是什么。 假設它是您的問題中使用的整數(而不是其他答案中所使用的數組),那么這里是不帶嵌套的.then()
的另一個改寫版本。
window.addEventListener('load', function() {
web3.eth.net.getId()
.then(networkId => networkId === 1 ? "0xQWERTYUIOPQWERTYUIOPQWERTY"
: "0x12345678901234567890123456")
.then(contractAddressRegistry => new web3.eth.Contract(contractAbiRegistry, contractAddressRegistry).methods.numberOfGames().call())
.then(numberOfGames => Promise.all(Array(numberOfGames).fill()
.map(_ => Promise.all([aSyncCallGetPropertyA(),
aSyncCallGetPropertyB(),
aSyncCallGetPropertyC()]))))
.then(function(games){
games = games.map(game => ({propertyA: game[0],
propertyB: game[1],
propertyC: game[2]}));
doSomethingWith(games);
});
});
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