Question

Is NSInvocation class not meant to be called via unit tests (for iPhone)?

My intent is to call a class’s method generically and since the method has more than 2 parameters, I can’t use [myTestClass performSelector:withObject:withObject]

Instead, I’m trying to use NSInvocation but as soon as I try to instantiate from NSInvocation class, I get the build error:

2009-12-31 11:12:16.380
otest[2562:903] ******* ABOUT TO CALL
NSInvocation
/Developer/Tools/RunPlatformUnitTests.include:
line 415: 2562 Bus error
“${THIN_TEST_RIG}”
“${OTHER_TEST_FLAGS}”
“${TEST_BUNDLE_PATH}”
/Developer/Tools/RunPlatformUnitTests.include:451:
error: Test rig
‘/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/
iPhoneSimulator3.1.2.sdk/Developer/usr/bin/otest’
exited abnormally with code 138 (it
may have crashed).

My class under test:

@implementation MyExampleClass
-(void)methodWithArgs:(NSString *)aValue 
          secondParam:(NSString *)aSecond 
          thirdParam:(NSString *)aThird
{
    NSLog(@"methodWithArgs reached");
}
-(void)methodBlank
{
    NSLog(@"methodBlank reached");
}
-(void)isTesting
{
    NSLog(@"isTesting reached");
}
@end

My unit test:

@interface MyClassTests : SenTestCase
{
}    
@end

@implementation MyClassTests

- (void)testNSInvocation
{   
    Class probeClass = NSClassFromString(@"MyExampleClass");
    if (probeClass != Nil) {        
      SEL selector = NSSelectorFromString(@"isTesting");

      NSMethodSignature *sig = [probeClass methodSignatureForSelector:selector];

      // the following line causes the error
      NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:sig];  

      // this variation also fails
      NSMethodSignature *sig2 = [probeClass 
      methodSignatureForSelector:@selector(methodWithArgs:secondParam:thirdParam:)];

      NSInvocation *inv2 = [NSInvocation invocationWithMethodSignature:sig2];   
    }   
}
@end

What’s a way to invoke a method with more than 2 parameters at run-time? Do I have to change the signature of the method so it only has 2 params? Is this a limitation of the unit-test framework?

Answer 1

The reason the above is failing is indeed due to an incorrect selector.

Instead of using “methodSignatureForSelector“, I needed to specify: “instanceMethodSignatureForSelector“

since the methods are instance methods.

However, both of your answers were helpful in tracking down the issue.