2

What's the appropriate way to update a struct via a function only if the parameters exist? For example

struct MyStruct {
  bytes32 someThing
  bytes32 someOtherThing
}

function updateStruct(bytes32 someThing, bytes32 someOtherThing) public {
  // get struct
  if (someThing) {
    struct.someThing = someThing;
  }
  if(someOtherThing) {
    struct.someOtherThing;
  }
}

I only want to update the fields of the struct if the argument is passed into the function. If it's null or undefined I don't want to update the struct with that value.

  • You can use somethig.length>0 for your if condition. – Prashant Prabhakar Singh Feb 4 '18 at 19:55
  • But what if its not bytes32 ? @PrashantPrabhakarSingh – pizzarob Feb 4 '18 at 19:55
  • I guess I will post a solution as comment will be too long. :) – Prashant Prabhakar Singh Feb 4 '18 at 19:58
  • I am going to create separate functions for updating each different value – pizzarob Feb 4 '18 at 21:58
  • If it's null or undefined - this is not Javascript. – goodvibration Jun 25 '18 at 4:06
0

So since your function has 2 parameters, you always have to pass 2 arguments. Now it depends on the type of function argument.

bytes32, you can use:

if(something.length != "")

If you have string, you can convert it to bytes32,

bytes memory testSomething= bytes(something);
if(testSomething.lenght > O)

If you have uint,

if(something > 0) 

In case of address:

if(something != 0x)
| improve this answer | |
  • For bytes32 the length is always 32, so you cannot use length to check for null with bytes32. But you can compare to zero if (something != 0) { } (the same trick applies with the address type). Also you cannot cast from bytes32 to bytes, if something is bytes32 then bytes(something) throws a compilation error. – Ismael Feb 4 '18 at 20:39
  • 1
    @Ismael I was not asking to convert bytes32 to bytes, I was saying if you have string params you can convert it to bytes and then check for length, ref: here. I need to check for bytes32, I thought this will be same as converting string to bytes 32. Please update the answer if you have a solution to check for empty value of bytes32. – Prashant Prabhakar Singh Feb 5 '18 at 4:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.