Delegate

Similar to a UITableView, BEMSimpleLineGraph uses a delegate to change the graph's appearance and receive events. Unlike the data source, you are not required to implement a delegate. Please refer to Getting Started - Setup for instructions on setting-up your delegate.

Graph Events

When the line graph starts or completes loading it will call one of the following delegate methods. You should not attempt to reload the graph's data source or change its layout while it is updating.

Graph Did Begin Loading

This method is sent to the delegate when the graph begins loading. The graph will begin loading after it is first initialized and when it is reloaded after initialization.

- (void)lineGraphDidBeginLoading:(BEMSimpleLineGraphView *)graph {
    // Prepare for loading
}

Graph Did Finish Loading

This method is sent to the delegate when the graph finishes loading. The graph is considered finished loading when all initial loading has been completed and the data source has been updated. Graph animations may still be taking place when this method is called.

- (void)lineGraphDidFinishLoading:(BEMSimpleLineGraphView *)graph {
    // Update interface after reloading the graph. Ensure the data source is synced-up.
}

WARNING Calling the graphSnapshotImage method before the graph finishes drawing and animating may result in a nil or partially rendered image of the graph. Please use lineGraphDidFinishDrawing to know when it is acceptable to use this API.

Graph Did Finish Drawing

This method is sent to the delegate when the graph finishes drawing and animating. The entrance animation time is used to calculate when the graph has finished animating, laying out subviews, and drawing. It is acceptable to use the graphSnapshotImage API after this method is called.

- (void) lineGraphDidFinishDrawing:(BEMSimpleLineGraphView *)graph {
    // Update any interface elements that rely on a full rendered graph
}

---

Popups

The delegate provides two methods which provide fine-grained control over graph popups.

Popup Suffix

Retrieves the optional suffix to append to the popup report. The popup suffix is a string which is appended to the numerical value of a popup. In the example below, a popup which read "26.7" would now read "26.7 miles".

- (NSString *)popUpSuffixForlineGraph:(BEMSimpleLineGraphView *)graph {
    return @"miles";
} 

Always Display Popup At Index

Optional method to always display specific popup labels on the graph. The alwaysDisplayPopUpLabels property must be set to YES for this method to have any affect. This method is called for each point on the graph, from left to right. Use the index parameter to determine which point the method is being called for.

- (BOOL)lineGraph:(BEMSimpleLineGraphView *)graph alwaysDisplayPopUpAtIndex:(CGFloat)index {
    if (index == 0 || index == 10) return YES;
    else return NO;
} 

---

Touch Events

The delegate provides two methods which provide fine-grained control over touch events.

Touched Graph at Closest Index

Sent to the delegate when the user starts touching the graph. The property enableTouchReport must be set to YES. The index parameter provides the closest index (X-axis) from the location the user is currently touching.

- (void)lineGraph:(BEMSimpleLineGraphView *)graph didTouchGraphWithClosestIndex:(NSInteger)index {
    // Update the interface to display relevant data
} 

Released Touch from Graph at Closest Index

Sent to the delegate when the user stops touching the graph. The index parameter provides the closest index (X-axis) to which the user last touched.

- (void)lineGraph:(BEMSimpleLineGraphView *)graph didReleaseTouchFromGraphWithClosestIndex:(CGFloat)index {
    // Update the interface to display relevant data
} 

---

X-Axis

Use the delegate to control spacing between x-axis labels. The numberOfGapsBetweenLabelsOnLineGraph: method is sent to the delegate to retrieve the number of free space between labels on the X-axis to avoid overlapping. Return the number of labels to "jump" between each displayed label on the X-axis. For example, returning '1' would mean that half of the labels on the X-axis are not displayed: the first is not displayed, the second is, the third is not etc. Returning '0' would mean that all of the labels will be displayed. Finally, returning a value equal to the number of labels will only display the first and last label.

- (NSInteger)numberOfGapsBetweenLabelsOnLineGraph:(BEMSimpleLineGraphView *)graph {
    return 1;
}

---

Y-Axis

Use the delegate to control the number of y-axis labels. The numberOfYAxisLabelsOnLineGraph: method is sent to the delegate when autoScaleYAxis is set to NO. Calculates the total height of the graph and evenly spaces the labels based on the graph height. Default value is 3. Return the number of labels displayed on the Y-axis.

- (NSInteger)numberOfYAxisLabelsOnLineGraph:(BEMSimpleLineGraphView *)graph {
    return 3;
}