我正在尝试创建一个函数,该函数将加载库(如果存在),或尝试安装它(如果不存在)。我遇到的问题是如何动态使用library
函数。 R使得这很难,因为library
函数不仅接受字符串。
例如,加载h2o:
library('h2o') ## This works
library(h2o) ## This also works...
但是,如果我有一个名为h2o
的变量?
h2o <- 'plyr'
library(h2o) ## imports the h2o package, not plyr
如何使用变量动态加载包?
答案 0 :(得分:3)
使用?library
选项进行h20 <- "plyr";
library(h20, character.only=TRUE);
sessionInfo();
来电。见#import <XCTest/XCTest.h>
#import "CertificateManager.h"
@interface UITests : XCTestCase
@end
-(void)testWelcomeScreen
{
//put the app into initial state
[[CertificateManager sharedInstance] resetApplication];
//... proceed with test
}
:
Undefined symbols for architecture i386:
"_OBJC_CLASS_$_CertificateManager", referenced from:
objc-class-ref in UITests.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)