:
Guys anyone of know
What exactly TransferFrom function does in real ?
Like we use in tokens

I don't understand
There is from, to , value..
But it can only be called by the owner of the smart contract right ?

only token owner or approved wallets can call transferfrom

So we have to manually enter
From:
To:
Value: ?

yes

you must be approved enough amount from from

Tell me real example which is happening in to crypto world

Yaa I got it but what is the need ?

real example? all tokens - FT/NFT use this kind of transfer

just assume you want to transfer your friend Alice's 10 dollars to some Bob,

I say Vitalik holds all the eth supply for instance
Why would he give someone this token
Rather than he can do it by himself

if Alice did not give you approval for 10 dollars, how can you do it?

Vitalk holds all eth right, but eth is not contract and we are talking about tokens

So like the owner approves defi platforms the amount of tokens which will be rewarded to users for staking ?

Basic example: a token holder approves some staking contract the ability to move their tokens...i.e. the staking contract "deposit" code calls transferFrom to move the tokens into the contract when called by the user

hmm, a bit different.. approve usually happens before stake transaction because defi contracts need to call transferFrom(your_account, its_own_account, amount)

Why just he cannot transfer the token amount ?
Rather approval

he can just transfer tokens directly, but that doesn't cause the smart contract to run any code (i.e. track his deposit, etc)

I am getting VM exception while processing transaction error

While using transferFrom

hard to say what the issue is without seeing the code, but check that the approval is correct, and that the from address balance is sufficient, etc.

@coffeeconverter

can you toNumber() those? Can't tell the bignumber values there

or toString() is fine too

100

is fromAccount == accounts[0] ?

Nope it's different acc

then why did you check your allowance against accounts[0] ?

Account [0] is owner

you need to have an allowance for sendingAccount to spend "from"'s tokens

in this case you're trying to transfer fromAccount's tokens as spendingAccount, so you should have an allowance for that...your code above checked accounts[0] which is not the one whose tokens are being moved in your example

so check tokenInstance.allowance(fromAccount, spendingAccount)

So this statement relies that fromAccount has given approval to spendingAccount
To transferFrom tokens?

yes

Yeah it worked find 👍🏽

nice