I want to write the following if - else logic in Velocity
If $var1 == NONE
( If $subvar1 != 'null'
return True
else
return Failed_Sub1)
Else
If $subvar2 != 'null'
return True
else
return Failed_Sub2
So basically $subvar2 is only evaluated if $var != NONE and $subvar1 is only evaluated if $var == NONE
I tried something like
#if($var1 != 'NONE')
#if($subvar2 != 'null')True
#{else}Failed_Sub2
#end
#else
#if($subvar1 != 'null')True
#{else}Failed_Sub1
#end
#end
But its returning nothing to me. What am I doing wrong?
Do you want to avoid null values or strings containing 'null'?
In velocity, you can check for nulls using any non assigned reference, for instance $null :
#if($var1 == $null)
...
Otherwise than that, your code looks fine and nested #if statements are definitely possible.
Here's the relevant documentation.
Related
So i want to compare three members of an array with as little code as possible. Heres what i did:
for(i in 0..2) {
if(board[i][0] == board[i][1] == board[i][2]) {
return true
} else if(board[0][i] == board[1][i] == board[2][i]) {
return true
}
}
(All of the values ar Char's FYI) But it didnt work. I get this error message "Operator '==' cant be applied to 'Boolean' and 'Char'". I also tried using .equals, but that just didnt work. Any ideas on what to do?
You can write a small function to keep it more readable and tidy, especially if You need to do that comparison often:
fun allEqual(vararg items: Any) : Boolean {
for(i in 1..(items.size-1)){
if(items[0] != items[i]) return false
}
return true
}
And invoke simply by comma separating values:
allEqual(board[i][0], board[i][1], board[i][2])
I don't know Kotlin specifically, but most* languages don't allow you to compare 3 values at the same time. What your error message is communicating is that your code ends up comparing
"Is board[i][0] equal to board[i][1]?" which is true/false (Boolean)
to
board[i][2], which is a Char.
*I don't know of any, but maybe there's one out there that does.
You have included this condition:
if(board[i][0] == board[i][1] == board[i][2])
Firstly, this one is compared: board[i][1] == board[i][2]
After comparing, it returns true. After that if logic converts to:
if(board[i][0] == true)
Now, board[i][0] is a char and you are trying to compare it to a boolean which is not possible. That's why you are getting this error.
You have to change the logic to:
if((board[i][0] == board[i][1]) && (board[i][1] == board[i][2]))
So, your code will be:
for(i in 0..2) {
if((board[i][0] == board[i][1]) && (board[i][1] == board[i][2])) {
return true
} else if((board[0][i] == board[1][i]) && (board[1][i] == board[2][i])) {
return true
}
}
Another approach:
for (i in 0..2) {
if (board[i].toSet().size == 1)
return true
else if (board.map { it[i] }.toSet().size == 1)
return true
}
As the others said, your first comparison returns Boolean, and the second compares Boolean to Char.
You can use an extension function, and transitivity to simplify things:
fun Any.equalsAll(vararg others: Any):Boolean
{
others.forEach {
if(it!=this)
return false
}
return true
}
and call:
if (board[0][i].equalsAll(board[1][i], board[2][i]))
In Objective-C, is
if(abc && def) allowed???
here abc is of BOOL type and def is of NSString type.
This condition is present in the code snippet I am going through. When will it return YES and when will it return FALSE?
The if statement will be true only if abc is unequal to NO and def is not nil.
The expression is equivalent to:
if (abc != 0 && def != 0) {
}
abc is not equal to 0 when it is unequal to NO. def is not equal to 0 when it is not nil.
if (abc && def) {
}
this condition will return YES if abc is not ZERO and def is also not nil (means it contains some not nil value). in either case it will return NO.
i hope you will understand this.
Guys what am I doing wrong?
if (numberstring.intValue <=15) {
rankLabel.text = #"A1";
}
else if (numberstring.intValue >16 && <=40){
rankLabel.text = #"A2";
}
I get an error on the "<=40" ..
You missed off a variable reference:
if (numberstring.intValue <=15) {
rankLabel.text = #"A1";
} // vv here vv
else if (numberstring.intValue >16 && numberstring.intValue <= 40){
rankLabel.text = #"A2";
}
As an optional extra, it looks like numberstring is an NSString object, which you are repeatedly converting to an integer in order to test various ranges. That operation is quite expensive, so you are better off doing the conversion once:
int value = [numberstring intValue];
if (value <=15) {
rankLabel.text = #"A1";
}
else if (value >16 && value <= 40){
rankLabel.text = #"A2";
}
Also note that the intValue method is not a property so I would avoid using the Objective-C 2.0 dot syntax to access it and use the normal method calling mechanism.
The && operator links two clauses together. However, each clause is independent, so each one has to be syntactically correct on its own if the other was removed. If you apply this rule to your condition, you can see that "<=40" is not syntactically correct on its own. Thus you need to reference the value being compared, as follows:
if (numberstring.intValue > 16 &&
numberstring.intValue <= 40) // this is syntactically correct on its own
int side1test;
NSLog(#"Is your triangle setup as in an Angle-Side-Angle? (Use 1 for Yes and 0 for No.)");
scanf(" %i", &side1test);
Returns "0" when the user enters a "y." However,
if (side1test != 1 && side1test != 0){
NSLog(#"Please use a '1' for YES and '0' for NO.");
}
Then does not catch.
The program drops into my else clause, and outputs all the NSLogs, skipping the scanf() commands, taking each of them as "0." What is wrong here?
I'm not a c++ dev but from googling that function returns the number of valid matches. If it returns 0 you should assume invalid input. side1test has not been set which is why it's 0.
Your code should probably be:--
int side1test;
NSLog(#"Is your triangle setup as in an Angle-Side-Angle? (Use 1 for Yes and 0 for No.)");
int result = 0;
while (result==0)
{
result =scanf(" %i", &side1test);
}
if (side1test != 1 && side1test != 0){
NSLog(#"Please use a '1' for YES and '0' for NO.");
}
I've responded to threads here (or at least commented) with answers containing code like this, but I'm wondering if it's good or bad form to write a series of if branches with one (or more) of the branches doing nothing in them, generally to eliminate checking for null in every branch.
An example (C# code):
if (str == null) { /* Do nothing */ }
else if (str == "SomeSpecialValue")
{
// ...
}
else if (str.Length > 1)
{
// ...
}
instead of:
if (str != null && str == "SomeSpecialValue")
{
// ...
}
else if (str != null && str.Length > 1)
{
// ...
}
And, of course, this is just an example, as I tend to use these with larger and more complex classes. And in most of these cases, a null value would indicate to do nothing.
For me, this reduces the complication of my code and makes sense when I see it. So, is this good or bad form (a code smell, even)?
I prefer doing it like this-
if (str != null)
{
if (str == "[NULL]")
{
// ...
}
else if (str.Length > 1)
{
// ...
}
}
I think you can always "reword" an if with an empty body into it's negation with a body, and that it looks better and makes more sense.
I would normally put a return or something like that in the first if:
void Foo()
{
if (str == null) { return; }
if (str == "SomeSpecialValue")
{
// ...
}
else if (str.Length > 1)
{
// ...
}
}
If you can't do this, because the function does something else after the if/else, I'd say it's time to refactor, and split the if/else part out into a separate function, from which you can return early.
It is indeed good to avoid the following, because it needlessly re-checks one of the conditions (the fact that the compiler will optimize this away is beside the point--it potentially makes more work for folks trying to read your code):
if (str != null && str == "SomeSpecialValue")
{
// ...
}
else if (str != null && str.Length > 1)
{
// ...
}
But it's also rather bizarre to do what you suggested, below:
if (str == null) { /* Do nothing */ }
else if (str == "SomeSpecialValue")
{
// ...
}
else if (str.Length > 1)
{
// ...
}
I say this is bizarre because it obfuscates your intent and defies the reader's expectations. If you check for a condition, people expect you to do something if it is satisfied--but you're not. This is because your intent is not to actually process the null condition, but rather to avoid a null pointer when you check the two conditions you're actually interested in. In effect, rather than having two conceptual states to handle, with a sanity provision (non-null input), it reads instead like you have three conceptual states to handle. The fact that, computationally, you could say there are three such states is beside the point--it's less clear.
The usual case approach in this sort of situation is as Oren A suggested--check for the null, and then check the other conditions within the result block:
if (str != null)
{
if (str == "SomeSpecialValue")
{
// ...
}
else if (str.Length > 1)
{
// ...
}
}
This is little more than a matter of readability-enhancing style, as opposed to an issue of code smell.
EDIT: However, if you're set on the do-nothing condition, I do very much like that you included a "do nothing" comment. Otherwise, folks might think you simply forgot to complete the code.
In this particular case I will return early and it makes code easier to read
if (string.IsNullOrEmpty(str)) { return; }
I like to put an explicit return statement.
Yes it is a code smell.
One indication is that you thought to ask this question.
Another indication is that the code looks incomplete- as if something should belong there. It may be readable sure, but it feels off.
When reading that code, an outsider has to stop for a second and use brainpower to determine if the code is valid/complete/correct/as intended/adjective.
user359996 hit the nail on the head:
I say this is bizarre because it obfuscates your intent and defies the reader's expectations.
Your first example is perfectly readable to me -- doesn't smell at all.
It all depends on context. If putting an empty if statement makes the code more readable, then go for that.
It's readable, whether it is good or bad depends upon what you are trying to achieve - generally long nested "goes-on-forever" type if statements are bad. Don't forget about static string methods baked into the framework: string.IsNullOrEmpty() and string.IsNullOrWhiteSpace().
Your if (str == null) { /* Do nothing */ } line is unusual, but does have one positive point: it is letting other developers know up front that you are deliberately doing nothing for that case, with your long if/else if structure your intentions could become unclear if you changed it to
if (str != null)
{
/* carry on with the rest of the tests */
}