why did patrick wrote += instead of =

[Sanskar-khandelwal]

it was = , but he changed it to += in editing, why ? I know answer += 1 is answer = answer + 1, but still please explain what below image means

[Nlferu]

Hello @Sanskar-khandelwal

We are simply updating value saved under addressToAmountFunded assigned for msg.sender. By updating I mean we are just adding new value, (Which has been sent by msg.sender) to already existing value saved under addressToAmountFunded to keep track of total sum of values sent by msg.sender. Let me know if it is a bit more clear for you now.

[murtaza1sol]

its nothing but

addressToAmountFunded[msg.sender] = addressToAmountFunded[msg.sender] + msg.value;

for example,
the mapping addressToAmountFunded{msg.sender] stored a value 10(say) and the msg.value = 5(say) then this line of code means

addressToAmountFunded[msg.sender] = 10 + 5;

addressToAmountFunded[msg.sender] = 15;

now the value in the msg.sender address will be 15 now next time when someone call that function which have that line of code and send some value let say X, then

addressToAmountFunded[msg.sender] = 15 + X;