I have a pretty long sqlite query:
const char *sql_query = "SELECT statuses.word_id FROM lang1_words, statuses WHERE statuses.word_id = lang1_words.word_id ORDER BY lang1_words.word ASC";
How can I break it in a number of lines to make it easier to read? If I do the following:
const char *sql_query = "SELECT word_id
FROM table1, table2
WHERE table2.word_id = table1.word_id
ORDER BY table1.word ASC";
I am getting an error.
Is there a way to write queries in multiple lines?
This question is related to
c
objective-c
You can also do:
NSString * query = @"SELECT * FROM foo "
@"WHERE "
@"bar = 42 "
@"AND baz = datetime() "
@"ORDER BY fizbit ASC";
Extending the Quote idea for Objective-C:
#define NSStringMultiline(...) [[NSString alloc] initWithCString:#__VA_ARGS__ encoding:NSUTF8StringEncoding]
NSString *sql = NSStringMultiline(
SELECT name, age
FROM users
WHERE loggedin = true
);
There's a trick you can do with the pre-processor.
It has the potential down sides that it will collapse white-space, and could be confusing for people reading the code.
But, it has the up side that you don't need to escape quote characters inside it.
#define QUOTE(...) #__VA_ARGS__
const char *sql_query = QUOTE(
SELECT word_id
FROM table1, table2
WHERE table2.word_id = table1.word_id
ORDER BY table1.word ASC
);
the preprocessor turns this into:
const char *sql_query = "SELECT word_id FROM table1, table2 WHERE table2.word_id = table1.word_id ORDER BY table1.word ASC";
I've used this trick when I was writing some unit tests that had large literal strings containing JSON. It meant that I didn't have to escape every quote character \".
GCC adds C++ multiline raw string literals as a C extension
C++11 has raw string literals as mentioned at: https://stackoverflow.com/a/44337236/895245
However, GCC also adds them as a C extension, you just have to use -std=gnu99
instead of -std=c99
. E.g.:
main.c
#include <assert.h>
#include <string.h>
int main(void) {
assert(strcmp(R"(
a
b
)", "\na\nb\n") == 0);
}
Compile and run:
gcc -o main -pedantic -std=gnu99 -Wall -Wextra main.c
./main
This can be used for example to insert multiline inline assembly into C code: How to write multiline inline assembly code in GCC C++?
Now you just have to lay back, and wait for it to be standardized on C20XY.
C++ was asked at: C++ multiline string literal
Tested on Ubuntu 16.04, GCC 6.4.0, binutils 2.26.1.
You could also go into XCode -> Preferences, select the Indentation tab, and turn on Line Wrapping.
That way, you won't have to type anything extra, and it will work for the stuff you already wrote. :-)
One annoying thing though is...
if (you're long on indentation
&& short on windows) {
then your code will
end up squished
against th
e side
li
k
e
t
h
i
s
}
I am having this problem all the time, so I made a tiny tool to convert text to an escaped multi-line Objective-C string:
http://multilineobjc.herokuapp.com/
Hope this saves you some time.
One more solution for the pile, change your .m file to .mm so that it becomes Objective-C++ and use C++ raw literals, like this:
const char *sql_query = R"(SELECT word_id
FROM table1, table2
WHERE table2.word_id = table1.word_id
ORDER BY table1.word ASC)";
Raw literals ignore everything until the termination sequence, which in the default case is parenthesis-quote.
If the parenthesis-quote sequence has to appear in the string somewhere, you can easily specify a custom delimiter too, like this:
const char *sql_query = R"T3RM!N8(
SELECT word_id
FROM table1, table2
WHERE table2.word_id = table1.word_id
ORDER BY table1.word ASC
)T3RM!N8";
An alternative is to use any tool for removing line breaks. Write your string using any text editor, once you finished, paste your text here and copy it again in xcode.
Source: Stackoverflow.com