我具有以下js代码结构;
Promise_1.then(function(){
for(){
Promise2.then(function(){
...
})
}
}).then(
Promise_3.then(function(){
for(){
Promise4.then(function(){
...
})
}
})
).then(
function(){
// SOME CODE
}
)
我想在上述承诺解决后执行一些代码。但是,在上述承诺得到解决之前,正在执行某些代码。我知道我可以在setTimeout()
中加上一些代码,这将解决SO上其他答案所建议的问题,但我认为这不是一个好主意。我正在使用的实际代码如下;
user_xp = 0
connections_blocks.methods.get_deposit_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
}, function (err, result) {
deposit_blocks = result
console.log(deposit_blocks)
deposit_blocks = deposit_blocks.split(",")
deposit_blocks.splice(0, 1)
for (i_ in deposit_blocks) {
console.log(deposit_blocks[i_])
user_xp + new_web3.eth.getBlock(deposit_blocks[i_]).then(function (deposit_block) {
user_xp = user_xp + deposit_block.gasUsed
console.log(user_xp)
})
}
}).then(
connections_blocks.methods.get_send_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
}, function (err, result) {
send_blocks = result
console.log(send_blocks)
send_blocks = send_blocks.split(",")
send_blocks.splice(0, 1)
for (i_ = 0; i_ < send_blocks.length; i_ = i_ + 2) {
console.log(send_blocks[i_])
user_xp + new_web3.eth.getBlock(send_blocks[i_]).then(function (send_block) {
user_xp = user_xp + send_block.gasUsed
console.log(user_xp)
})
}
})).then(
setTimeout(function () {
console.log(user_xp)
xp = document.getElementById('xp')
xp.innerHTML = "XP:" + user_xp
},1000)
)
在上面的代码中,我只是使用setTimeout()
来解决我的问题。但是我希望代码仅在上述承诺得到解决时才自动执行。没有任何简单的方法可以在JS中做到这一点,而不必在函数中添加承诺并使其更加复杂。
UPDATE
[我正在使用以下web3的功能从实体的智能合约中获取数据,该合约实际上返回了一个以promiseValue
为数据的承诺
myContract.methods.myMethod([parameters).call(options,[callback])
我假设Promise_1和Promise_3的解析将等待回调完成。如果是这种情况,这应该可以工作。
user_xp = 0
connections_blocks.methods.get_deposit_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
}, function (err, result) {
deposit_blocks = result
console.log(deposit_blocks)
deposit_blocks = deposit_blocks.split(",")
deposit_blocks.splice(0, 1)
// array to hold the promises
const subPromises = []
for (i_ in deposit_blocks) {
console.log(deposit_blocks[i_])
subPromises.push(new_web3.eth.getBlock(deposit_blocks[i_]))
}
// waiting for all promises to resolve
Promise.all(subPromises).then(function (deposit_block) {
user_xp = user_xp + deposit_block.gasUsed
console.log(user_xp)
})
})
.then(
connections_blocks.methods.get_send_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
}, function (err, result) {
send_blocks = result
console.log(send_blocks)
send_blocks = send_blocks.split(",")
send_blocks.splice(0, 1)
const subPromises = []
for (i_ = 0; i_ < send_blocks.length; i_ = i_ + 2) {
console.log(send_blocks[i_])
subPromises.push(
new_web3.eth.getBlock(send_blocks[i_])
)
}
Promise.all(subPromises).then(function (send_block) {
user_xp = user_xp + send_block.gasUsed
console.log(user_xp)
})
})
)
.then(function () {
console.log(user_xp)
xp = document.getElementById('xp')
xp.innerHTML = "XP:" + user_xp
})
您的代码存在的问题
对您的actual代码进行以下更改-我假设没有节点样式回调,该函数将返回一个承诺,该承诺将解析为将传递给节点样式回调的result
(在此代码中删除)
user_xp = 0
return connections_blocks.methods.get_deposit_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
})
.then(function (result) {
var promises = []
deposit_blocks = result
console.log(deposit_blocks)
deposit_blocks = deposit_blocks.split(",")
deposit_blocks.splice(0, 1)
for (i_ in deposit_blocks) {
console.log(deposit_blocks[i_])
promises.push(
new_web3.eth.getBlock(deposit_blocks[i_]).then(function (deposit_block) {
user_xp = user_xp + deposit_block.gasUsed
console.log(user_xp)
})
)
}
return Promise.all(promises)
})
.then(function () {
return connections_blocks.methods.get_send_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
})
})
.then(function (result) {
var promises=[]
send_blocks = result
console.log(send_blocks)
send_blocks = send_blocks.split(",")
send_blocks.splice(0, 1)
for (i_ = 0; i_ < send_blocks.length; i_ = i_ + 2) {
console.log(send_blocks[i_])
promises.push(
new_web3.eth.getBlock(send_blocks[i_]).then(function (send_block) {
user_xp = user_xp + send_block.gasUsed
console.log(user_xp)
})
)
}
return Promise.all(promises)
})
.then(function () {
console.log(user_xp)
xp = document.getElementById('xp')
xp.innerHTML = "XP:" + user_xp
})
作为附加的“奖励”,我相信代码可以简化为
return connections_blocks.methods.get_deposit_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
})
.then(result => Promise.all(result.split(",").slice(1).map(deposit_block => new_web3.eth.getBlock(deposit_block)
.then(deposit_block => deposit_block.gasUsed)
})
.then(gasUsed1Array => connections_blocks.methods.get_send_blocks(current_email).call({
from: new_web3.eth.Contract.defaultAccount
})
.then(result => Promise.all(result.split(",").slice(1).filter((v, i) => !(i%2)).map(send_blocks => new_web3.eth.getBlock(send_block)
.then(send_block => send_block.gasUsed)
)))
.then(gasUsed2Array => [...gasUsed1Array, ...gasUsed2Array])
)
.then(results => {
user_xp = results.reduce((a, b) => a + b);
console.log(user_xp)
xp = document.getElementById('xp')
xp.innerHTML = "XP:" + user_xp
})