collect2：ld返回1退出状态

| ld \“ build / Debug-iphonesimulator / Cloudmade Map.app/Cloudmade Map \”正常i386 cd /用户/ MPDEV /文档/ cloudmade2 setenv MACOSX_DEPLOYMENT_TARGET 10.6 setenv PATH \“ / Developer / Platforms / iPhoneSimulator.platform / Developer / usr / bin：/ Developer / usr / bin：/ usr / bin：/ bin：/ usr / sbin：/ sbin \” /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 -arch i386 -isysroot /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.3.sdk -L / Users / MPDEV / Documents / cloudmade2 / build / Debug-iphonesimulator -L / Users / MPDEV / Documents / cloudmade2 / libs / Proj4 -L / Users / MPDEV / Documents / cloudmade2 / libs / CloudMade -L / Users / MPDEV / Documents / cloudmade2 / libs / route-我-F / Users / MPDEV / Documents / cloudmade2 / build / Debug-iphonesimulator -filelist \“ / Users / MPDEV / Documents / cloudmade2 / build / cloudmade2.build / Debug-iphonesimulator / cloudmade2.build / Objects-normal / i386 / Cloudmade Map.LinkFileList \“ -mmacosx-version-min = 10.6 -lMapView -lProj4 -lCloudMadeApi -ObjC -all_load -Xlinker -objc_abi_version -Xlinker 2 -framework Foundation -framework UIKit -framework CoreGraphics -lsqlite3 -framework QuartzCore -lstdc ++。6- o \“ /用户/ MPDEV /文档/ cloudmade2 / build / Debug-iphonesimulator / Cloudmade Map.app/Cloudmade Map \” 未定义符号：   \“ _ OBJC_CLASS _ $ _ RMDBMapSource \”，引用自：       cloudmade2ViewController.o中的objc-class-ref-to-RMDBMapSource ld：找不到符号 collect2：ld返回1退出状态 我该如何解决这个问题？我尝试环顾四周，但没有找到解决方法的答案。