htmlの選択ボックスのプレースホルダー作成に関する質問

@interface TestMem: NSObject {
TestObject *m_testObject ; // member variable
TestObject *testObject ; // member variable
}

// assign
-(void)setTestObject :(id)newValue{
testObject= newValue;
}
// retain
-(void)setTestObject :(id)newValue{
if (testObject!= newValue) {
[testObject release];
testObject= [newValue retain];
}
}
// copy
-(void)setTestObject :(id)newValue{
if (testObject ! = newValue) {
[testObject release];
testObject = [newValue copy];
}
}

self.testObject = [[testObject alloc] init]; // wrong reatin twice
testObject = [NSArray objectbyindex:0]; // wrong not safe, no retain later release will be wrong

NSString *testString = [NSString stringWithFormat:@"test" ];