安装 facebook sdk 后，当我构建我的项目时，它显示：
ld: warning: directory not found for option '-F/Users/liyuanliu/Library/Developer/Xcode/DerivedData/c5-dsovqtraubbdgxbqrmiexjmlysxq/Build/Products/Debug-iphonesimulator/Bolts'
ld: warning: directory not found for option '-F/Users/liyuanliu/Library/Developer/Xcode/DerivedData/c5-dsovqtraubbdgxbqrmiexjmlysxq/Build/Products/Debug-iphonesimulator/FBSDKCoreKit'
ld: warning: directory not found for option '-F/Users/liyuanliu/Library/Developer/Xcode/DerivedData/c5-dsovqtraubbdgxbqrmiexjmlysxq/Build/Products/Debug-iphonesimulator/FBSDKLoginKit'
ld: warning: directory not found for option '-F/Users/liyuanliu/Library/Developer/Xcode/DerivedData/c5-dsovqtraubbdgxbqrmiexjmlysxq/Build/Products/Debug-iphonesimulator/FBSDKShareKit'
ld: framework not found Bolts
clang: error: linker command failed with exit code 1 (use -v to see invocation)
但是当我安装 facebook 和 bolts 时，它显示我安装成功：
pod install
Analyzing dependencies
Downloading dependencies
Using Bolts (1.8.4)
Using FBSDKCoreKit (4.14.0)
Using FBSDKLoginKit (4.14.0)
Using FBSDKShareKit (4.14.0)
Using Firebase …char *s;
char buf [] = "This is a test";
s = strchr (buf, 't');
if (s != NULL)
printf ("found a 't' at %s\n", s);
printf("%c\n",*s);
printf("%c\n",*s++);
printf("%c\n",*s++);
printf("%c\n",*s++);
printf("%c\n",*s++);
此代码输出:
found a 't' at test
t
t
e
s
t
Program ended with exit code: 0
在我看来,*s应该t和*s ++应该是e.但为什么他们在这段代码中有相同的价值呢？