If I pass Vertex structure to shader attribute then it works, but if I'm passing one dimensional array, then it doesn't work

gistfile1.m

typedef struct {
    float Position[3];
    float Color[4];
} Vertex;

const Vertex Vertices[] = {
        {{1, -1, -7}, {1, 0, 0, 1}},
        {{1, 1, -7}, {0, 1, 0, 1}},
        {{-1, 1, -7}, {0, 0, 1, 1}},
        {{-1, -1, -7}, {0, 0, 0, 1}}
};

...
    const float  cylinderVertices[] = {
        0.8,    -0.8,   -7,
        0.8,    0.8,    -7,
        -0.8,   -0.8,   -7,
        -0.8,   0.8,    -7,
    };


    GLuint vertexBuffer;
    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, 4, cylinderVertices, GL_STATIC_DRAW);

...

    glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 4, 0);

    glDrawArrays(GL_LINE_STRIP, 0, 4);

...