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// GTMDebugSelectorValidation.h
// This file should only be included within an implimation file. In any
// function that takes an object and selector to invoke, you should call:
// GTMAssertSelectorNilOrImplementedWithArguments(obj, sel, @encode(arg1type), ..., NULL)
// or
// GTMAssertSelectorNilOrImplementedWithReturnTypeAndArguments(obj, sel, @encode(returnType), @encode(arg1type), ..., NULL)
// This will then validate that the selector is defined and using the right
// type(s), this can help catch errors much earlier then waiting for the
// selector to actually fire (and in the case of error selectors, might never
// really be tested until in the field).
// Copyright 2007-2008 Google Inc.
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#import <stdarg.h>
#import "GTMDefines.h"
static void GTMAssertSelectorNilOrImplementedWithReturnTypeAndArguments(id obj, SEL sel, const char *retType, ...) {
// verify that the object's selector is implemented with the proper
// number and type of arguments
va_list argList;
va_start(argList, retType);
if (obj && sel) {
// check that the selector is implemented
_GTMDevAssert([obj respondsToSelector:sel],
@"\"%@\" selector \"%@\" is unimplemented or misnamed",
NSStringFromClass([obj class]),
const char *expectedArgType;
NSUInteger argCount = 2; // skip self and _cmd
NSMethodSignature *sig = [obj methodSignatureForSelector:sel];
// check that each expected argument is present and of the correct type
while ((expectedArgType = va_arg(argList, const char*)) != 0) {
if ([sig numberOfArguments] > argCount) {
const char *foundArgType = [sig getArgumentTypeAtIndex:argCount];
_GTMDevAssert(0 == strncmp(foundArgType, expectedArgType, strlen(expectedArgType)),
@"\"%@\" selector \"%@\" argument %d should be type %s",
NSStringFromClass([obj class]),
(argCount - 2),
// check that the proper number of arguments are present in the selector
_GTMDevAssert(argCount == [sig numberOfArguments],
@"\"%@\" selector \"%@\" should have %d arguments",
NSStringFromClass([obj class]),
(argCount - 2));
// if asked, validate the return type
if (retType && (strcmp("gtm_skip_return_test", retType) != 0)) {
const char *foundRetType = [sig methodReturnType];
_GTMDevAssert(0 == strncmp(foundRetType, retType, strlen(retType)),
@"\"%@\" selector \"%@\" return type should be type %s",
NSStringFromClass([obj class]),
#define GTMAssertSelectorNilOrImplementedWithArguments(obj, sel, ...) \
GTMAssertSelectorNilOrImplementedWithReturnTypeAndArguments((obj), (sel), "gtm_skip_return_test", __VA_ARGS__)
#else // DEBUG
// make it go away if not debug
#define GTMAssertSelectorNilOrImplementedWithReturnTypeAndArguments(obj, sel, retType, ...) do { } while (0)
#define GTMAssertSelectorNilOrImplementedWithArguments(obj, sel, ...) do { } while (0)
#endif // DEBUG
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