enforce

Enforces that the given value is true. If the given value is false, an exception is thrown. The

msg - error message as a string
dg - custom delegate that return a string and is only called if an exception occurred
ex - custom exception to be thrown. It is lazy and is only created if an exception occurred

template enforce(E : Throwable = Exception)
T enforce(T value, Dg dg)
T enforce(T value, Throwable ex)
T
enforce
(
T
)
(
T value
,
lazy Throwable ex
)

Parameters

value T: The value to test.
ex Throwable: The exception to throw if the value evaluates to false.

Return Value

Type: T

value, if cast(bool) value is true. Otherwise, depending on the chosen overload, new Exception(msg), dg() or ex is thrown.

Note: enforce is used to throw exceptions and is therefore intended to aid in error handling. It is not intended for verifying the logic of your program. That is what assert is for. Also, do not use enforce inside of contracts (i.e. inside of in and out blocks and invariants), because contracts are compiled out when compiling with -release.

If a delegate is passed, the safety and purity of this function are inferred from Dg's safety and purity.

Examples

import core.stdc.stdlib : malloc, free;
import std.conv : ConvException, to;

// use enforce like assert
int a = 3;
enforce(a > 2, "a needs to be higher than 2.");

// enforce can throw a custom exception
enforce!ConvException(a > 2, "a needs to be higher than 2.");

// enforce will return it's input
enum size = 42;
auto memory = enforce(malloc(size), "malloc failed")[0 .. size];
scope(exit) free(memory.ptr);

assertNotThrown(enforce(true, new Exception("this should not be thrown")));
assertThrown(enforce(false, new Exception("this should be thrown")));

assert(enforce(123) == 123);

try
{
    enforce(false, "error");
    assert(false);
}
catch (Exception e)
{
    assert(e.msg == "error");
    assert(e.file == __FILE__);
    assert(e.line == __LINE__-7);
}

Alias your own enforce function

import std.conv : ConvException;
alias convEnforce = enforce!ConvException;
assertNotThrown(convEnforce(true));
assertThrown!ConvException(convEnforce(false, "blah"));

enforce

Parameters

Return Value

Examples

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