QGIS-2.8-PyQGISDeveloperCookbook-en(20)

为开发人员准备的文档,涵盖QGIS的多种功能实现和代码。

tohaveaQgsVectorLayerobject

5.3.1Accessingattributes

Attributescanbereferredtobytheir

name.

Alternatively,attributescanbereferredtobyindex.Thisiswillbeabitfasterthanusingthename.Forexample,

togetthe rstattribute:

5.3.2Iteratingoverselectedfeatures

ifyouonlyneedselectedfeatures,youcanusetheselectedFeatures()methodfromvectorlayer:

AnotheroptionistheProcessingfeatures()method:

Bydefault,thiswilliterateoverallthefeaturesinthelayer,incasethereisnoselection,orovertheselected

featuresotherwise.NotethatthisbehaviorcanbechangedintheProcessingoptionstoignoreselections.