如何在glShaderSource中将String作为GLchar **（char **）参数传递？

Question

我有一个存储在String值中的着色器：

    var myShader = 
    "    attribute vec4 a_position;" +
    "    void main() {" +
    "    gl_Position = a_position;" +
    "    }"

    glShaderSource(shader, GLsizei(1), myShader, nil)

函数glShaderSource具有绑定签名：

    func glShaderSource(shader: GLuint, count: GLsizei, string: UnsafePointer<UnsafePointer<GLchar>>, length: UnsafePointer<GLint>)

当我尝试将着色器String直接传递给glShaderSource时，我收到错误消息：

    'String' is not convertible to 'UnsafePointer<UnsafePointer<GLchar>>'

如何正确传递字符串？ （xCode版本6.1（6A1052d））

Answer 1

经过半天的搜索，我发现工作解决方案没有编译错误，内存访问不良失败了：

var cStringSource = (code as NSString).UTF8String
glShaderSource(shader, GLsizei(1), &cStringSource, nil)

Answer 2

在OpenGLs Swift实现中，CLchar被类型化为CChar。进行如下转换：

var shaderString: String = "here's a String"
let cstring = shaderString.cStringUsingEncoding(NSUTF8StringEncoding)
glShaderSource(shader, GLsizei(1), UnsafePointer(cstring), nil)

Answer 3

斯威夫特3：

let shaderStringUTF8 = shaderString.cString(using: String.defaultCStringEncoding)
var shaderStringUTF8Pointer = UnsafePointer<GLchar>(shaderStringUTF8)

glShaderSource(shaderHandle, GLsizei(1), &shaderStringUTF8Pointer, nil)