Difference between #import header file with <filename> and "filename" [duplicate] - objective-c
I'm wondering what decides whether you're allowed to use <Header.h> or "Header.h" when you're importing files in Objective-C. So far my observation has been that you use the quote marks "" for files in your project that you've got the implementation source to, and angle brackets <> when you're referencing a library or framework.
But how exactly does that work? What would I have to do to get my own classes to use the brackets? Right now Xcode will not allow me to do that for my own headers.
Also, by looking in some frameworks headers, I see that the headers reference each other with <frameworkname/file.h>. How does that work? It looks a lot like packages in Java, but as far as I know, there is no such thing as a package in Objective-C.
Objective-C has this in common with C/C++; the quoted form is for "local" includes of files (you need to specify the relative path from the current file, e.g. #include "headers/my_header.h"), while the angle-bracket form is for "global" includes -- those found somewhere on the include path passed to the compiler (e.g. #include <math.h>).
So to have your own headers use < > not " " you need to pass either the relative or the absolute path for your header directory to the compiler. See "How to add a global include path for Xcode" for info on how to do that in Xcode.
See this MSDN page for more info.
In C, the convention is that header files in <> bracket are searched in 'system' directories and "" in user or local directories.
The definition of system and local is a bit vague, I guess. I believe it looks in system directories in include path or in CPPFLAGS for <header.h>, and local directory or directory specified with -I to compiler are searched for "header.h" files.
I assume it works similarly for Objective-C.
To import your own classes using "< >" you have to put the header files (*.h) in the lib folder of compiler or set a SYSTEM VARIABLES ponting to your lib folder.
#import <> vs ""
<Name.h> - Angle brackets tells to preprocessor to search in a special pre-designated system's directories. For example you import systems headers like <UIKit/UIKit.h> or added frameworks
"Name.h" - Quotation marks tells to preprocessor to search in a current directory. If a header was not found the preprocessor try to use <Name.h>. Usually you should use it with your project's files
Just stumbled upon the same problem, there are 2 types of search paths is Xcode:
User Header Search Paths
Header Search Paths
If you add your own include folders into Header Search Paths, you can use angled brackets without any problem.
Or set Always Search User Path to YES so you can use angle brackets.
With angle brackets e.g. <Foundation/Foundation.h> you import system files.
You use double quotes "Person.h" to import local files (files that you created) and to tell the compiler where to look for them.
If this is an Xcode project and you want to include it in a framework, have the header file you want to included open. Then, open Xcode's rightmost tab and under "Target Membership", click on the framework you want your file to available from.
e.g. If your framework is AlphaTools and your header, AceHeader, then you'll select AlphaTools on Target Membership so you can access < AlphaTools/AceHeader.h
WHAT IS HEADER FILE ?
Header files contain definitions of functions and variables which can be incorporated into any C program by using the pre-processor #include statement. Standard header files are provided with each compiler, and cover a range of areas, string handling, mathematical, data conversion, printing and reading of variables.
Ex- #include it contain the information about input like scanf(),and out put like printf() function and etc in a compiler.
INCLUDE
1) #INCLUDE:-
It is a pre-processor that process before process of main function.
The main work of pre-processor is to initialize the environment of program i.e that is the program with the header file.
2).h:-
(Header file) A header file is a file with extension .h which contains C function declarations and macro definitions and to be shared between several source files.
Q) There are two types of header files: the files that the programmer writes and the files that come with your compiler ?
A)In a angular brackets
Angular-bracket form is for "global" includes -- those found somewhere on the include path passed to the compiler (e.g. #include)
It is used for using of library function which is all ready define in compiler.
In C the convention is that header files in <> bracket are searched in 'system' directories
B) Quote marks:- “header.h”
quoted form is for "local" includes of files (you need to specify the relative path from the current file, e.g. #include "headers/my_header.h")
In C the convention is that header files in " " are searched in user or local directories.
In it one file to be included in another .(FILE INCLUSION).
It can be used in two cases:
Case 1: If we have a very large program, the code is best divided int several different files,each containing a set of related functions.
Case 2: There are some functions and micros definitions that we need at most in all programs that we write.
Ex
Related
file strings requires and filename and output variable in cmake
target_link_libraries(${PROJECT_NAME}
serializer
iothub_client
iothub_client_mqtt_transport
umqtt
aziotsharedutil
ssl
crypto
curl
ssl..... utils)
Hello there , I am working on a project where I have a large set of libraries, and have use it like it (shown above). but instead of hardcoding these libraries explicitly,i want write it in a one line.
now I want to write it in a one line for linking, so specifically, what I have tried in the root level I have created a file called "library.lst" and in this .lst file I am giving the path of that library
build/src/con/shared/virtual/serializer/serializer.a"
build/src/con/shared/virtual/iothub_client/iothub_client.a"
build/src/con/shared/virtual/umqtt/ umqtt.a"
build/src/con/shared/virtual/utils/utlis.a
## write for every library
I am placing this .lst file in the folder called "filelist", e.g filelist/Library.lst where it will take all the libraries and will link.
so what I wrote this In each camkelists.txt where this library used by writing
file(STRINGS ${filelist} library) ,
target_link_libraries(${PROJECT NAME} ${library}),
but when I am running this script I an getting the errors like
"error:- "file strings requires and filename and output variable",
and I also have creates build.sh file where I am giving the path of it
"-D"filelist=%FILELISTSPATH%\library.lst"
" so could you please help me here and also need some explanation on it to understand it in a better way.Thanks in advance.
Cmake script problems find_path
I have put these two lines in my Findglm.cmake file to point to the headers for this header library.
find_path(glm_INCLUDE_DIR NAMES glm.hpp matrix_transform.hpp type_ptr.hpp PATHS
${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm ${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm/gtc
${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm/gtx ${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2glm/core)
set(glm_INCLUDE_DIRS ${glm_INCLUDE_DIR})
However when I generate my Xcode project it says that it cannot locate matrix_transform.hpp and type_ptr.hpp
I have played around with this some more it appears to only find the first argument I am wondering if I am using find path wrong ?
I am using cmake 2.8.8 darwinports.
The find_path() command returns single directory. In your case, it's the first dir, which contains the first file.
If this glm will be always located in your source dir, it would be sufficient to do
include_directories(${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm
${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm/gtc
${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm/gtx
${CMAKE_SOURCE_DIR}/libs/glm-0.9.3.2/glm/core)
The find_path() is used to determine dir somewhere outside of your project.
Compilation C, C++, Objective-C et Objective-C++ on Mac
I use CPLUS_INCLUDE_PATH environment variable to compile .cpp files and it works fine to find .h files. But it's not ok to compile ObjC or ObjC++. Do you know the good one variable. Thanks.
From the manual page: CPATH C_INCLUDE_PATH CPLUS_INCLUDE_PATH OBJC_INCLUDE_PATH Each variable’s value is a list of directories separated by a special character, much like PATH, in which to look for header files. The special character, "PATH_SEPARATOR", is target‐ dependent and determined at GCC build time. For Microsoft Windows‐ based targets it is a semicolon, and for almost all other targets it is a colon. CPATH specifies a list of directories to be searched as if specified with −I, but after any paths given with −I options on the command line. This environment variable is used regardless of which language is being preprocessed. The remaining environment variables apply only when preprocessing the particular language indicated. Each specifies a list of directories to be searched as if specified with −isystem, but after any paths given with −isystem options on the command line. In all these variables, an empty element instructs the compiler to search its current working directory. Empty elements can appear at the beginning or end of a path. For instance, if the value of CPATH is ":/special/include", that has the same effect as −I. −I/special/include.
difference between "file.h" and <file.h> import statements [duplicate]
This question already has answers here: Closed 12 years ago. Possible Duplicate: Obj C - #import < > and “ ” This may be a simple question, but googling it is difficult. What's the difference between following two statements? #import "GrowlDisplayPlugin.h" #import <GrowlDisplayPlugin.h> They work in different ways for me, so I thought it's about time I understand what I'm doing. In particular, the second one says 'No such file or directory' and the first one following linking error. Undefined symbols: "_OBJC_METACLASS_$_GrowlDisplayPlugin" Thank you
" are used for local files. That means files in the current directory or in directories specified by the -iqoute flag for the GCC compiler. < and > are used for system files found in the folders of your path. /usr/include is probably one of them. The -I flag can be used to specify more directories to search when looking for those files.
Using <> imports from the library search paths. Using "" imports the file from your user search paths (usually just the directory containing your project)
The difference is in the order, in which the compiler searches different folders for files. The "fine.h" form gives precedence to the current folder (the one where the containing source file is). The <> form searches the system include folder first.
#import using angle brackets < > and quote marks " "
I'm wondering what decides whether you're allowed to use <Header.h> or "Header.h" when you're importing files in Objective-C. So far my observation has been that you use the quote marks "" for files in your project that you've got the implementation source to, and angle brackets <> when you're referencing a library or framework. But how exactly does that work? What would I have to do to get my own classes to use the brackets? Right now Xcode will not allow me to do that for my own headers. Also, by looking in some frameworks headers, I see that the headers reference each other with <frameworkname/file.h>. How does that work? It looks a lot like packages in Java, but as far as I know, there is no such thing as a package in Objective-C.
Objective-C has this in common with C/C++; the quoted form is for "local" includes of files (you need to specify the relative path from the current file, e.g. #include "headers/my_header.h"), while the angle-bracket form is for "global" includes -- those found somewhere on the include path passed to the compiler (e.g. #include <math.h>). So to have your own headers use < > not " " you need to pass either the relative or the absolute path for your header directory to the compiler. See "How to add a global include path for Xcode" for info on how to do that in Xcode. See this MSDN page for more info.
In C, the convention is that header files in <> bracket are searched in 'system' directories and "" in user or local directories. The definition of system and local is a bit vague, I guess. I believe it looks in system directories in include path or in CPPFLAGS for <header.h>, and local directory or directory specified with -I to compiler are searched for "header.h" files. I assume it works similarly for Objective-C.
To import your own classes using "< >" you have to put the header files (*.h) in the lib folder of compiler or set a SYSTEM VARIABLES ponting to your lib folder.
#import <> vs "" <Name.h> - Angle brackets tells to preprocessor to search in a special pre-designated system's directories. For example you import systems headers like <UIKit/UIKit.h> or added frameworks "Name.h" - Quotation marks tells to preprocessor to search in a current directory. If a header was not found the preprocessor try to use <Name.h>. Usually you should use it with your project's files
Just stumbled upon the same problem, there are 2 types of search paths is Xcode: User Header Search Paths Header Search Paths If you add your own include folders into Header Search Paths, you can use angled brackets without any problem.
Or set Always Search User Path to YES so you can use angle brackets.
With angle brackets e.g. <Foundation/Foundation.h> you import system files. You use double quotes "Person.h" to import local files (files that you created) and to tell the compiler where to look for them.
If this is an Xcode project and you want to include it in a framework, have the header file you want to included open. Then, open Xcode's rightmost tab and under "Target Membership", click on the framework you want your file to available from. e.g. If your framework is AlphaTools and your header, AceHeader, then you'll select AlphaTools on Target Membership so you can access < AlphaTools/AceHeader.h
WHAT IS HEADER FILE ? Header files contain definitions of functions and variables which can be incorporated into any C program by using the pre-processor #include statement. Standard header files are provided with each compiler, and cover a range of areas, string handling, mathematical, data conversion, printing and reading of variables. Ex- #include it contain the information about input like scanf(),and out put like printf() function and etc in a compiler. INCLUDE 1) #INCLUDE:- It is a pre-processor that process before process of main function. The main work of pre-processor is to initialize the environment of program i.e that is the program with the header file. 2).h:- (Header file) A header file is a file with extension .h which contains C function declarations and macro definitions and to be shared between several source files. Q) There are two types of header files: the files that the programmer writes and the files that come with your compiler ? A)In a angular brackets Angular-bracket form is for "global" includes -- those found somewhere on the include path passed to the compiler (e.g. #include) It is used for using of library function which is all ready define in compiler. In C the convention is that header files in <> bracket are searched in 'system' directories B) Quote marks:- “header.h” quoted form is for "local" includes of files (you need to specify the relative path from the current file, e.g. #include "headers/my_header.h") In C the convention is that header files in " " are searched in user or local directories. In it one file to be included in another .(FILE INCLUSION). It can be used in two cases: Case 1: If we have a very large program, the code is best divided int several different files,each containing a set of related functions. Case 2: There are some functions and micros definitions that we need at most in all programs that we write. Ex