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- (void)addObserver:(__weak NSObject *)observer forContext:(void *)context {
NSValue *valueContext = [NSValue valueWithPointer:context];
dispatch_sync(self.queue, ^{
[self.trampolines setObject:observer forKey:valueContext];
});
}
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原文地址：http://www.cnblogs.com/AlvinCrash/p/5601165.html
