Undefined symbols for architecture i386: "_crc32", referenced from:——crc链接错误

　　有时候用别人的框架，你会碰到下面的错误，很是吓人，什么玩意，我怎么看不懂！！！

Undefined symbols for architecture i386:
  "_RELEASE", referenced from:
      -[DemoAnnotationView dealloc] in DemoAnnotationView.o
  "_crc32", referenced from:
      -[ZipArchive addFileToZip:newname:] in ZipArchive.o
      _unzReadCurrentFile in unzip.o
      _zipWriteInFileInZip in zip.o
  "_deflate", referenced from:
      _zipWriteInFileInZip in zip.o
      _zipCloseFileInZipRaw in zip.o
  "_deflateEnd", referenced from:
      _zipCloseFileInZipRaw in zip.o
  "_deflateInit2_", referenced from:
      _zipOpenNewFileInZip3 in zip.o
  "_get_crc_table", referenced from:
      _unzOpenCurrentFile3 in unzip.o
      _zipOpenNewFileInZip3 in zip.o
  "_iconv", referenced from:
      _qr_code_data_list_extract_text in libzbar.a(qrdectxt.o)
  "_iconv_close", referenced from:
      _qr_code_data_list_extract_text in libzbar.a(qrdectxt.o)
  "_iconv_open", referenced from:
      _qr_code_data_list_extract_text in libzbar.a(qrdectxt.o)
  "_inflate", referenced from:
      _unzReadCurrentFile in unzip.o
  "_inflateEnd", referenced from:
      _unzCloseCurrentFile in unzip.o
  "_inflateInit2_", referenced from:
      _unzOpenCurrentFile3 in unzip.o
　　......

　　IOS编译时有时出现这样的错误，要注意，错误不在Undefined for architecture i386，而是下面下划线开头的变量没定义，此时需要导入libz到项目即可。

　　Build Phases ——> Link Binary With Libraries 中导入libz.1.2.5.dylib即可。

　　提醒：下次如果再碰到crc链接错误，请把libz.dylib加入到项目中去。