QVariant to int8 and uint8_t

[MrLibya]

Hello
I'm reading some value from DB and put it into varables with type ( uint8_t , int8 )
e.g

nationality = rec.value(rec.indexOf("nationality")).toUInt();

but i get this

warning: implicit conversion loses integer precision: 'uint' (aka 'unsigned int') to 'int8_t' (aka 'signed char')

so should i use static cast here ? or there's another way .

[raven-worx]

@MrLibya said in QVariant to int8 and uint8_t:

so should i use static cast here ? or there's another way .

will result in the same warning.
the variable nationality should be of the of the target type (uint) instead of int8_t, thats what this warning means

[aha_1980]

@MrLibya The warning clearly states, that your destination data type is too small to take values an uint can hold. Also, you mix signed and unsigned integers.

The very correct way would be (assuming nationality is uint8_t:

bool ok = false;
uint value = rec.value(rec.indexOf("nationality")).toUInt(&ok);
if (ok && value < 255)
  nationality = uint8_t(value); // or static_cast<uint8_t>
else
  nationality = 0;

If nationality is signed, i.e. int8_t (does that make sense?!), you should use toInt() instead and adjust the range checks.

Regards

[MrLibya]

@raven-worx
i know what's that mean but this varable can't get value more then 127 so i don't want use uint for small values .

[MrLibya]

@aha_1980
the value from the db always postive and less then 127 so i only need to read it from the db but the function dosen't have toInt8 so this why i use toUInt , i'm asking is there a function for Int8 or i only should use static cast .

[aha_1980]

@MrLibya said in QVariant to int8 and uint8_t:

the value from the db always postive and less then 127

Then either use uint or the approach I explained above. There is no need to use an signed integer like int8_tl

[MrLibya]

@aha_1980
Well i'm only trying to not use memory more then i need , like why i use 4 Bytes and i can use 1 Byte ?

[Christian Ehrlicher]

@MrLibya said in QVariant to int8 and uint8_t:

like why i use 4 Bytes and i can use 1 Byte ?

Do you use them in an array or another struct? If not due to the alignment it will at least use 32 bits for it.
Don't try to optimize without measuring first.

[MrLibya]

@Christian-Ehrlicher
i'm using them in class

[Christian Ehrlicher]

First your class members are not optimal aligned for low memory usage so why do you care for this specific member and secondly - this class is so big that a max of 3 more bytes don't count in any way.

[MrLibya]

@Christian-Ehrlicher
ok thanks :)